Leveling; getting unexpected results

Question: I have spent hours reading up on the leveling algorithm and trying various alternative approaches but I have a problem I simply can't figure out.  I'm using MSP 2016.
My schedule consists of around 1250 tasks made up of about 250 separate and independent projects each with about 5 tasks.  Each project and its related tasks has been assigned a unique Priority Score; eg Project A and all its tasks are 950 whereas Project B and all its tasks are 949.  However, the higher ranked project may be further down the ID hierarchy; eg Project A with score 950 may have starting ID of 525 whereas Project B with score of 949 may start at ID 275.
My leveling options are Month by Month with Can split tasks.  Initially I chose Priority, Standard as the leveling order.
This worked pretty well but I found a few tasks that were inexplicably leveled to start AFTER lower priority unrelated tasks, even where there appeared to be available resource to start on or sooner after the original Start date.
In a particular case the lower ranked task was delayed by leveling to start on 1 Jan and finish on 31 Jan, whereas the higher ranked task, which had a longer duration of 2.5 months and which should have started on 17 Jan was delayed to 1 Feb.
So that is my first question; how could this happen?  Why was the lower priority task not split to allow the higher priority task to use the available resources and start on 17 Jan?  In fact, why was this task delayed at all when there appears to be sufficient available resource?
I then sorted my plan by Priority and then ID, and then permanently updated the ID values to this new sort order.  Then I tried leveling by ID only.  The results were similar (not surprisingly) but not exactly the same, and still had the problem with some tasks not being prioritised correctly.
I then changed the leveling order to Standard and found that the problem task now started on the correct date but now had a longer split mid task and that many higher priority tasks were delayed more than previously.
I have tried to replicate these issues in a simple generic plan but have been unable to do so, so I assume they are an artifact of the complexity of my plan.  However despite its size it really is not complex as each group of 5 or so tasks is independent of all other groups.
This is really causing me some problems, can anyone shed any light on the causes of these apparent inconsistencies?
Thanks
Eric
Answer: This is not really a possible canonical answer but more of a suggestion.  I have found that a tool's leveling feature consistently produces results that were both unexpected and seemingly weird.  I personally avoid allowing the tool to level my project's schedule.  I instead use it to see possible solutions for leveling that I may or may not use as I manually level the schedule.  In other words, use what it does that makes sense and ignore what it does that makes no sense, then punch your baseline.  Also, I avoid trying to get to "perfect" leveling with zero over- or under-utilization since work is always probabilistic.  It's a precision that is only valid until two minutes after you start work, then it's off.
Comment: David, thanks for the suggestions.  However, because of the way I am trying to use MSP I really need leveling to "work".  Specifically, I am using MSP to produce a resource leveled schedule for 250 unrelated projects that all use the same generic resources; eg Project Engineer, Field Engineer.  I treat each type of resource as interchangeable within that type, input the quantity of each type in each month and then click Level All.
Comment: (did not realise I can't do a carriage return when inputtting a comment) This almost works, but not quite, or at least it is not consistently reliable.

Leveling; getting unexpected results


How to make an animation play in the blender game engine?

Question: Ok so I have created a character and rigged it and when I hit the play button for the animation it plays just fine.
I have set up the logic bricks multiple time yet whenever I hit P to play the animation never plays.  I cant seem to find my mistake if anyone could help me it would be much appreciated.
edit: here's the link
Answer: First you had the logic bricks on the wrong object. You needed the Action actuator on the Armature not the mesh object, because it is the armature that is animated.
Your second problem was the mirror modifier (I applied it). The mirror modifier was causing the animation to not play in the BGE. Just another one of the differences between the game engine and blender.
In general you should not have any modifiers or transforms (scale or rotation) on your objects in the BGE.
Your working blend file.
Comment: Thank you so much for your help i was so puzzled by this but i am very new to the bge so i guess this is something that is learned along the way, thank you for taking the time to look at it and solve my problem:)


Installing packages in multiple systems

Question: I have to install some packages in 5 Ubuntu system in my office. There, bandwidth is limited. So, is there any way to install it in one system & copy to other, so that all works fine? All systems are fresh install.
Answer: Maybe not an exact duplicate but the solutions for "How can I install software offline?" should help you.
Since bandwidth is an issue you might also want to consider setting up one of the machines as a caching deb proxy so you don't have to manually copy files around, that way if you install a package once it will be cached on your LAN.
Answer: Simply copy the relevant deb archives from /var/cache/apt/archives of the first machine to /var/cache/apt/archives of every machine
Then run the same installation command given on the first machine on every other machine.
If already there, deb archives will not be downloaded, and only installation take place.
Answer: You could also use aptoncd.
This will create an iso image for you containing an offline repository of all the apps installed on the first computer.
You could then use the aptoncd on the other 5 computers to copy the apps to cache for Software Center to use or add the cd as a repository to synaptic package manager.

Installing packages in multiple systems


Free batch converter/normalizer to/from CAF (Core Audio Format) file

Question: Is there any free tool capable of doing the job?
Answer: You didn't supply very much information, such as your OS and your desired output format, so I can not give you a detailed answer.
CAF is a container format that can support several audio formats, but Apple Lossless (ALAC) is probably the most common.
ffmpeg can decode ALAC in CAF:
ffmpeg -i input.caf output.wav

This can be turned into a "batch" command with a Bash "for loop".
for f in *.caf; do ffmpeg -i "$f" "${f%.caf}.wav"; done

sox can be added to this example to normalize your audio:
for f in *.caf; do ffmpeg -i "$f" -f sox - | sox --norm=-3 -t sox - "${f%.caf}.wav"; done

As usual, using a recent ffmpeg is recommended since development is so active. See the FFmpeg download page for various methods to acquire it.
Comment: I think that is exactly what I needed. I did a little Googling, and it turns out that ffmpeg and sox are compatible with most platforms, included mine (Mac OS X), thanks very much
Answer: Sox is great as some above mentioned, I'd check out Sample Manager by audiofile engineering though. It's cheap and awesome. I use it nearly every day.
Answer: OSX?
AFCONVERT(1)              BSD General Commands Manual

NAME
     afconvert -- Audio File Convert

SYNOPSIS
     afconvert [-h] src_audiofile dest_audiofile

DESCRIPTION
     Audio File Convert will convert a source audio file to a new audio file
     with the specified file and data types

Comment: hi georgi - this doesn't cover off the normalisation part of the question.
Comment: true.. i didn't pay attention to the "normaliser" part of the question. that said, the accepted answer also uses another third party tool (sox) to normalise the sounds. i meant to point out that ffmpeg is overkill.


How to translate "tenure"?

Question: Tenure is a permanent academic position.
The position is very safe, as it is far more complicated to fire a tenured professor than an employee who has a permanent contract.
There are variations, and for example in Finland there is no "true tenure": permanent professors have as much job security as a permanent plumber.
If you want definiteness, you can restrict this question to tenure as understood in most of the US today.
Is there a good Latin word or phrase for "tenure" or "tenured" that would capture the sense of permanence and immutability?
Comment: If not, I sense an opportunity for a wonderful invented word!
Comment: @DukeZhou Since there have been no answers so far, I would be happy to see any new coinages as well. Perhaps something with *munus*, *officium*, or *magistratus*?
Answer: In Italy, quoting the website of the European University Institute,

apart from 'assegno di ricerca', 'professore a contratto', and 'ricercatore di tipo B', all other positions are tenure or tenure-track.

In particular any position of Associate Professor ('professore associato') is a tenure-track or tenured one, and that of Full Professor ('professore ordinario') is tenured after a probationary period ('professore straordinario').
We may generalise saying that "tenure" (somewhat if not perfectly) corresponds to titolarità di cattedra, and is usually translated as such - literally "ownership of a professorship chair". Since titularis is an attested Late Latin word, we may translate tenure as titularitas cathedrae. This German website describes Paul Fridolin Kehr as titularis cathedrae historiae medii aevi Gottingensis, so "tenured professor" may be translated as (professor/docens) titularis cathedrae.
Answer: To make sure the word is understood correctly as referring to the academic concept of tenure, I suggest taking a word that is easily connected to the English "tenure".
My suggestion is tentura, "holding" (roughly), from the past participle tentus of tenere, "to hold, master, guard, or stay".
I think this captures the idea quite nicely is easy to recognize.
The derivation of tentura < tenere is similar to censura < censere and cultura < colere; it should not be confused with a future participle.
For a comparison of the two, see this question on whether cultura is a future participle.
Comment: @TomCotton No, it's not a participle but a derived noun. It isn't supposed to mean "tenured" but the concept "tenure" itself. I added some examples of the phenomenon to my answer.
Comment: Oh, dear, of course you are right!
Comment: But isn't that the n. pl. of the future participle? If it's a noun you want (i.e., rather than the adj. 'tenured'), then the standard Decl. 4 noun would be _tentus_.
Answer: Central-European have a similar concept where the important step is a habilitation. habilitatio (medieval) - making qualified or eligible, declaratio habilitatis - declaration of qualification. After a habilitation one becomes a docent - docens - teaching (a lecturer).
Answer: The closest Latin word in meaning is probably immobilis, 'immoveable, unalterable' — though it is usually applied to some physical entity.  However, if that isn't acceptable, then indemobilis might be reasonably derived from the verb demoveo, which can certainly be applied to individuals.
[Such positions are found in England, defending against dismissal in all but extreme circumstances, but there's no general rule about them. The principle still seems to be applied in some universities, but not nowadays in the Civil Service, which until a few decades ago spoke of officers not as tenured, but 'with establishment'.]

How to translate "tenure"?


Tricks that help boom operators to memorize lines of dialogue

Question: Hello fellow boom operators. I was wondering if you had any advice on how to memorize dialogue. During my last shoot we had 5 kid protagonists and a few other actors talking in one scene. While preparing for the master shot I had to memorize more than one page of script Dialogue with everyone speaking in no particular order. I managed to do that by memorizing words that were build with the first letters of each actors name. It was very hard not to switch letters around with words like MNMEMTAM..
How do you do it?
Answer: I've found that somehow just really digging into the scene and story helps with that. If you get really involved in the story, and the conversation, then the cues are often fairly natural. Bill asks Clara a question, Clara responds, etc. There are always the hard to remember ones, interjections, stuff like that. And of course when the actors are ad libbing a bit, it gets tricky. If you can keep an eye on the actors' chins in your peripheral vision (no staring head on, that's weird :p), that can often also be a good cue for when someone is about to speak. Aside from that, script-wise, try to focus on the beginning and ending of the lines. That's the important part for you.
Comment: Yes, everything you wrote makes perfect sense. The problem is that there can group situations where dialogue consists mostly of statements, and there is too much distance between the actors, hence not enough time to wait for the usual signs of someone starting to talk. I have never encountered these problems before, but believe me its very hard to get every cue right, especially during the first takes.
Comment: Spot on. For long, multi-characters scenes (especially when actors don't repeat scripts word-for word) I find it handy to memorise just the core intention of each line. For example:
"Let's talk about serious stuff"
"I'm disctracted by my work"
"Pay attention to me"
Answer: I assign the actors numbers from left to right and then memorize the number sequence! So you can end up with something like 3,1,3,2,3,1 and I find that easier than looking for cues. Other than that, knowing the script like the back of your hand!
Answer: If you are looking for mnemonics, look up what memory champions use. The main thing is thinking of a route that's already in your long term memory; your bedroom, the road to your grandma, or whatever. It's kind of like a memory palace, but differs (and excells) in that it's not a made up place and is easy to remember/picture in your head.
Along the route you place images representing what you need to remember. In this case I guess it would be cues. The more vivid/crazy the better. So for example if you put a flirty Joseph Stalin in your bed, a hockey player harvesting maple syrup from the door to your bedroom, a panda and a dragon dancing by the door to your house, and uncle Sam checking your mailbox, then you know that the largest countries in the world (including water area, and excluding Antarctica) are Russia, Canada, China, and the United States.
I haven't read it, but apparently Moonwalking with Einstein is good if you want to learn more.


Why is addition as fast as bit-wise operations in modern processors?

Question: I know that bit-wise operations are so fast on modern processors, because they can operate on 32 or 64 bits on parallel, so bit-wise operations take only one clock cycle. However addition is a complex operation that consists of at least one and possibly up to a dozen bit-wise operations, so I naturally thought it will be 3-4 times slower. I was surprised to see after a simple benchmark that addition is exactly as fast as any of the bit-wise operations(XOR, OR, AND etc). Can anyone shed light on this?
Comment: https://en.wikipedia.org/wiki/Carry-lookahead_adder also https://www.cs.umd.edu/class/sum2003/cmsc311/Notes/Comb/lookahead.html
Comment: Yep, multiplication was pretty fast in my tests too. It was only around 2x slower than addition, while division was around 30x (!) times slower.
Comment: fwiw, [multiplication isn't much slower](https://stackoverflow.com/a/24886154/1475548)
Comment: Compact overview of state-of-the-art parallel prefix tree adders: A Taxonomy of Parallel Prefix Networks by David Harris: http://pages.hmc.edu/harris/research/taxonomy.pdf
Comment: More elaborated: PhD Jun Chen's doctoral thesis "Parallel-prefix structures for binary and modulo {2n−1, 2n, 2n+1} adders" http://digital.library.okstate.edu/etd/Chen_okstate_0664D_10070.pdf
Answer: Addition is fast because CPU designers have put in the circuitry needed to make it fast.  It does take significantly more gates than bitwise operations, but it is frequent enough that CPU designers have judged it to be worth it.  See https://en.wikipedia.org/wiki/Adder_(electronics).
Both can be made fast enough to execute within a single CPU cycle.  They're not equally fast -- addition requires more gates and more latency than a bitwise operation -- but it's fast enough that a processor can do it in one clock cycle.  There is a per-instruction latency overhead for the instruction decoding and control logic, and the latency for that is significantly larger than the latency to do a bitwise operation, so the difference between the two gets swamped by that overhead.  AProgrammer's answer and Paul92's answer explain those effects well.
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackexchange.com/rooms/59454/discussion-on-answer-by-d-w-why-is-addition-as-fast-as-bitwise-operations-in-mo).
Answer: There are several aspects.

The relative cost of a bitwise operation and an addition.  A naive adder will have a gate-depth which depend linearly of the width of the word.  There are alternative approaches, more costly in terms of gates, which reduce the depth (IIRC the depth then depend logarithmically of the width of the word).  Others have given references for such techniques, I'll just point out that difference is also less important than what it may seem just considering the cost of the operation because of the need of control logic which add delays.
Then there is the fact that processors are usually clocked (I'm aware of some research or special purpose non clocked designs, but I'm not even sure that some are available commercially).  That means that whatever the speed of an operation is, it will take at an integer multiple of the clock cycle.
Finally there is the micro-architectural considerations: are you sure that you measure what you want? Nowadays, processors tend to be pipelined, multi-scalar, with out-of-order execution and whatever else.  That means that they are able to execute several instructions at the same time, at various stage of completion.  If you want to show by measurements that an operation takes more time that another, you have to take take those aspect in consideration as their goal is to hide those difference.  You may very well have the same throughput for addition and bitwise operations when using independent data but a measure of the latency or introducing dependencies between the  operations may show otherwise.  And you have also to be sure that the bottleneck of your measure is in the execution, and not for instance in the memory accesses.
Comment: +1. Yes, most processors are clocked, but a few [clockless CPUs](https://en.wikipedia.org/wiki/clockless_CPU) are commercially available.
Comment: SIMD integer add is often lower throughput than SIMD boolean, though, even though they usually have the same latency.  Intel CPUs from PentiumII through Broadwell can only run vector-int adds (e.g. `paddw`) at 2 per clock, but booleans (like `pand`) at 3 per clock.  (Skylake puts a vector adder on all three vector execution ports.)
Comment: @supercat The Pentium 4 did something like this, with a double-speed (relative to the rest of the processor) ALU that would have the low 16 or 32 bits ready for a subsequent operation a half-cycle before the upper half's bits.
Comment: *are you sure that you measure what you want?*  In this case, the OP's conclusion from the measurements happens to be correct for the vast majority of CPUs.  Addition is so common that superscalar CPUs have add units on all execution ports, and booleans are so cheap to implement (in transistor count) that they're also present on all ports.  So add and booleans almost always have the same throughput (e.g. 4 per clock in Intel Haswell).
Comment: Another possibility is that a processor might store a 64-bit register as one 16-bit piece and three 17-bit pieces, where the extra bits of each piece holding a deferred carry from below.  An addition which is followed by a bitwise operation or a store might require 1-2 extra cycles to propagate the carry, but an addition which is followed by another addition would not.  Further, in the "store" case, the extra propagation time may delay the performance of the store, but there would be no need for code to "wait" for it.
Comment: It's also worth the design effort to make it single-cycle latency for the critical path of a dependency chain.  This requires a single-cycle adder and efficient forwarding of outputs to inputs (bypassing write-back to registers).  All x86 CPUs that Agner Fog has measured have single cycle latency for ADD (see [his instruction tables](http://agner.org/optimize)), except for Pentium4 where ADD has 0.5 cycle latency (thanks to double-clocked ALUs, as @Jeffrey points out).  A chain of dependent additions can execute at 2 per clock on P4.  (Or 1 per clock on everything else).
Answer: CPUs operate in cycles. At each cycle, something happens. Usually, an instruction takes more cycles to execute, but multiple instructions are executed at the same time, in different states.
For example, a simple processor might have 3 steps for each instruction: fetch, execute and store. At any time, 3 instructions are being processed: one is being fetched, one is being executed and one stores its results. This is called a pipeline and has in this example 3 stages. Modern processors have pipelines with over 15 stages. However, addition, as well as most of the arithmetic operations, are usually executed in one stage (I am speaking about the operation of adding 2 numbers by the ALU, not about the instruction itself - depending on the processor architecture, the instruction might require more cycles for fetching arguments from memory, performing conditionals, storing results to memory).
The duration of a cycle is determined by the longest critical path. Basically, it's the longest amount of time necessary for some stage of the pipline to complete. If you want to make the CPU faster, you need to optimize the critical path. If reducing the critical path per se is not possible, it can be split into 2 stages of the pipeline, and you are now able to clock your CPU at almost twice the frequency (assuming there is not another critical path that prevents you from doing this). But this comes with an overhead: you need to insert a register between the stages of the pipeline. Which means that you don't really gain 2x speed (the register needs time to store the data), and you have complicated the whole design.
There are already quite efficient methods for performing addition (e.g. carry lookahead adders) and addition is not a critical path for the processor speed, thus is makes no sense splitting it into multiple cycles.
Also, note that while it might seem complicated for you, in hardware things can be done in parallel very fast.
Comment: The big overhead from longer pipelines is more cycles to recover from a branch misprediction!  Spending transistors to buffer data between stages is minor these days. Even a simple pipelined CPU has to be fetching / decoding ahead of instructions that are actually executing.  If the CPU discovers that the front-end was working on the wrong code because a branch went a different way than it predicted (or some other mis-speculation), it has to throw away that work and start from the correct instruction.  Things only get worse with superscalar out-of-order CPUs that can have many insns in flight.
Answer: Processors are clocked, so even if some instructions can clearly be done faster than others, they may well take the same number of cycles.
You'll probably find that the circuitry required to transport data between registers and execution units is significantly more complicated than the adders.
Note that the simple MOV (register to register) instruction does even less computation than bitwise logic, yet both MOV and ADD usually take one cycle. If MOV could be made twice as fast, CPUs would be clocked twice as fast and the ADDs would be two cycles.
Comment: Summary of the discussion: some out-of-order CPUs handle MOV specially with register-renaming, with effectively zero latency.  See [Can x86's MOV really be "free"? Why can't I reproduce this at all?](https://stackoverflow.com/questions/44169342/can-x86s-mov-really-be-free-why-cant-i-reproduce-this-at-all) for the full details of what MOV really costs.
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackexchange.com/rooms/59349/discussion-on-answer-by-james-hollis-why-is-addition-as-fast-as-bitwise-operatio).
Answer: Addition is important enough to not have it wait for a carry bit to ripple through a 64-bit accumulator: the term for that is a carry-lookahead adder and they are basically part of 8-bit CPUs (and their ALUs) and upwards.  Indeed, modern processors tend to need not much more execution time for a full multiplication either: carry-lookahead is actually a really old (and comparatively affordable) tool in a processor designer's toolbox.
Comment: Integer multiplication is definitely higher latency and lower throughput than ADD on x86.  But it is amazingly fast considering how many adders it takes to build a fast multiplier: e.g. on Intel since Nehalem, and AMD since Ryzen, 8/16/32/64-bit scalar integer multiply is 3 cycle latency, with one per 1c throughput (one fully-pipelined execution unit).  This sucks compared to ADD throughput of 3 or 4 per clock, but is amazing compared to 9 cycle IMUL latency in Intel Pentium P5.  Things are similar for SIMD: vector-int multiply is higher latency and lower throughput than add, but still fast.
Comment: So yes, multiply used to be much more expensive relative to other instructions than it is now.  Avoiding it at a cost of more than 2 instructions is usually not worth it, and sometimes not even a 2-instruction substitute is worth it (e.g. with a shift+add `lea` instruction).
Answer: I think you'd be hard pressed to find a processor that had addition taking more cycles than a bitwise operation. Partly because most processors must carry out at least one addition per instruction cycle simply to increment the program counter. Mere bitwise operations aren't all that useful.
(Instruction cycle, not clock cycle - e.g. the 6502 takes a minimum of two clock cycles per instruction due to being non-pipelined and not having an instruction cache)
The real concept you may be missing is that of the critical path: within a chip, the longest operation that may be performed within one cycle dictates, at the hardware level, how fast the chip may be clocked.
The exception to this is the (rarely used and hardly commercialised) asynchronous logic, which really does execute at different speeds depending on logic propagation time, device temperature etc.
Comment: It's not user-controllable bitwise operations, but some instructions on the 8086 (eg. [clearing the interrupt flag](http://zsmith.co/intel_c.html#cli)) took fewer cycles than an integer addition.  More abstractly, a RISC system where all the instructions are one word in size could use a simple binary counter for the PC, which would be a much faster circuit than a general-purpose adder.
Comment: Addition on the program counter tends to be very simple compared to an addition arithmetic instruction, because one of the operands is small (either an instruction size, or a relative jump offset which is also size-limited)
Comment: 6502 was pipelined - it read the first byte of the next instruction during the last cycle of the previous one. Otherwise fetch/decode/execute would have been at least three cycles.
Answer: At the gate level, you are correct that it takes more work to do addition, and thus takes longer.  However, that cost is sufficiently trivial that doesn't matter.
Modern processors are clocked.  You cannot do instructions at anything except multiples of this clock rate.  If the clock rates were pushed higher, to maximize the speed of the bitwise operations, you would have to spend at least 2 cycles on addition.  Much of this time would be spent waiting around because you didn't really need the full 2 cycles worth of time.  You only needed 1.1 (or some number like that).  Now your chip adds slower than everyone else on the market.
Worse, the mere act of adding or doing bitwise operations is only one tiny part of what is going on during a cycle.  You have to be able to fetch/decode instructions within a cycle.  You have to be able to do cache operations within a cycle.  Lots of other things are going on on the same timescale as the simple addition or bitwise operation.
The solution, of course, is to develop a massively deep pipeline, breaking these tasks up into tiny parts that fit into the tiny cycle time defined by a bitwise operation.  The Pentium 4 famously showed the limits of thinking in these deep pipeline terms.  All sorts of issues arise.  In particular branching gets notoriously difficult because you have to flush the pipeline once you have the data to figure out which branch to take.
Answer: Modern processors are clocked: Every operation takes some integral number of clock cycles. The designers of the processor determine the length of a clock cycle. There are two considerations there: One, the speed of the hardware, for example measured as the delay of a single NAND-gate. This depends on the technology used, and on tradeoffs like speed vs. power usage. It is independent of the processor design. Two, the designers decide that the length of a clock cycle equals n delays of a single NAND-gate, where n might be 10, or 30, or any other value.
This choice n limits how complex operations can be that can be processed in one cycle. There will be operations that can be done in 16 but not in 15 NAND delays. So chosing n = 16 means such an operation can be done in a cycle, choosing n = 15 means it can't be done.
The designers will chose n so that many important operations can be just about done in one, or maybe two or three cycles. n will be chosen locally optimal: If you replaced n with n-1, then most operations would be a bit faster, but some (those that really need the full n NAND delays) would be slower. If few operations would slow down, so that overall program execution is faster on average, then you would have picked n-1. You could also have picked n+1. That makes most operations a bit slower, but if you have many operations that can't be done within n delays but can be done within n+1 delays then it would make the processor overall faster.
Now your question: Add and subtract are so common operations that you want to be able to execute them in a single cycle. As a result, it doesn't matter that AND, OR etc. could execute faster: They still need that one cycle. Of course the unit "calculating" AND, OR etc has a lot of time to twiddle its thumbs, but that can't be helped.
Note that it's not just whether an operation can be done within n NAND-delays or not: An addition for example can be made faster by being a bit clever, still faster by being very clever, still a bit faster by investing extraordinary amounts of hardware, and at last a processor can have a mixture of very fast very expensive and a bit slower and cheaper circuits, so there is the possiblity to make one operation just about fast enough by spending more money on it.
Now you could make the clock speed so high / the cycle so short that only the simple bit operations execute in one cycle and everything else in two or more. That would most likely slow the processor down. For operations that take two cycles, there is usually overhead to move an incomplete instruction from one cycle to the next, so two cycles doesn't mean you have twice as much time for execution. So to do the addition in two cycles, you couldn't double the clock speed.
Answer: Let me correct a few things that were not mentioned that explicitely in your existing answers:

I know that bitwise operations are so fast on modern processors, because they can operate on 32 or 64 bits on parallel,

This is true. Labeling a CPU as "XX" bit usually (not always) means that most of its common structures (register widths, addressable RAM etc.) are XX bits in size (often "+/- 1" or somesuch). But in regards to your question, you can safely assume that a CPU with 32 bit or 64 bit will do any basic bit operation on 32 or 64 bits in constant time.

so bitwise operations take only one clock cycle.

This conclusion is not necessarily the case. Especially CPUs with rich instruction sets (google CISC vs. RISC) can easily take more than one cycle for even simple commands. With interleaving, even simples commands might break down into fetch-exec-store with 3 clocks (as an example).

However addtion is a complex operation

No, integer addition is a simple operation; subtraction as well. It is very easy to implement adders in full hardware, and they do their stuff as instantaneously as basic bit operations.

that consists of at least one and possibly up to a dozen bitwise operations, so I naturally thought it will be 3-4 times slower.

It will take up 3-4 times as many transistors, but in comparison to the big picture that is neglectible.

I was surprised to see after a simple benchmark that addition is exactly as fast as any of the bitwise operations(XOR, OR, AND etc). Can anyone shed light on this?

Yes: integer addition is a bitwise operation (with a few more bits than the others, but still). There is no need to do anything in stages, there is no need for complicated algorithms, clocks or anything else.
If you wish to add more bits than your CPU architecture, you will incur a penalty of having to do it in stages. But this is on another level of complexity (programming language level, not assembly/machine code level). This was a common problem in the past (or today on small embedded CPUs). For PCs etc., their 32 or 64 bits are sufficient for the most common data types for this to start to become a moot point.
Comment: It's interesting to note that reducing the time cost of addition from O(N) to O(sqrt(N)) does not significantly increase the required number of transistors or routing complexity (each stage just needs to let one carry wire sneak in from below, and there need to be sqrt(N) extra merging stages.  The time cost can be reduced to O(lgN) at a cost of O(lgN) transistors, but in many cases it may be helpful to process something like a 64-bit addition as e.g. eight 8-bit adds (using sqrtN forwarding) joined with three layers of merging logic, rather than as 64 1-bit adds with six layers of merging.
Comment: Yeah, adders are fairly simple. What's really impressive is modern x86 CPUs with a fully pipelined 3-cycle latency 64-bit integer *multiplier*.  (e.g. `imul rax, rcx` has 3c latency, and one per 1c throughput on Intel Sandybridge-family, and AMD Ryzen).  Even 64-bit full-multiplication (producing the 128 bit result in rdx:rax) has the same latency and throughput, but is implemented as 2 uops (which run in parallel on different ports).  (See http://agner.org/optimize/ for instruction tables and an excellent microarch guide).
Comment: *[add-with-carry] is on another level of complexity (programming language level, not assembly/machine code level*.  It depends on the language.  A C compiler targeting a 16-bit CPU has to emit add/adc for you when it compiles addition of two `uint32_t` values.  This is still relevant today for int64_t on 32-bit targets.  AVR is an 8-bit RISC microcontroller, so 32-bit integers require 4 instructions: https://godbolt.org/g/wre0fM
Comment: Yes, @PeterCordes, that is what I meant, I've clarified my sentence a little bit.


Guitar Chord Recognition Algorithm?

Question: Whats a good digital signal processing algorithm that is good on guitar chords? Since Fast Fourier Transform I think only is accurate on single notes played on the guitar but not notes that are played simultaenously (i.e. chords).
Thanks!
Comment: On what basis do you think the FFT is inacurrate in your case?
Comment: Ask the guys from Melodyne: http://www.youtube.com/watch?v=jFCjv4_jqAY
Answer: The short answer is that you need much more than one algorithm. Good chord recognition methods could more aptly be described as "systems", but usually they are indeed based on an initial transform to the frequency domain (most often DFT).
If you want a chord representaton of the song similar to this
<code>C G Am F7 F6 C ...
</code>
then this is actually a problem that is slightly removed from recognising the notes in a piece of audio. In fact, there are two problems (roughly speaking):

finding which pitches are present at any time
grouping these pitches over time so as to be able to assign a chord label to a time interval.

It turns out that the way you transform from the time domain (normal audio) to the frequency domain (spectral representation) is only of limited importance. It's very important what you do afterwards, and often sophisticated probabilistic models (similar to those in speech recognition: HMMs, DBNs, ...) are used to tackle this problem.
Try google scholar "chord transcription", or "chord detection", or "chord labelling" for advanced research in this area.
Most of these approaches use a discrete Fourier transform (DFT) to create the initial spectrogram. During further processing, too, they tend to differ only slightly, though different time-series smoothing techniques have been used: hidden Markov models, dynamic Bayesian networks, support vector machines (SVMstruct), and conditional random fields -- among others.
The most advanced transcribers use automatic tuning, key information, bass note information, and information of the metric position to improve the results. My thesis (Chapter 2) gives a nice overview.
Open source chord detection algorithms:

Chordino at http://isophonics.net/nnls-chroma
Chordata at http://clam-project.org/
LabROSA Chord Recognition http://labrosa.ee.columbia.edu/projects/chords/

Hope this helps.
Comment: +1 for a good answer and for being able to reference your own thesis in the answer.
Comment: i'm having a difficulty about using LabROSA Chord Recognition, can you guide me how to use it ? i use the terminal command, extractFeaturesAndTrain_svm and doChordID_svm, but it is unrecognized
Answer: There are some reasonably successful tools that use the DFT (FFT), but they do lots of processing after calculating the DFT.
Try this link for a summary the current state of the art, or google "Chordino" or "Chordata" for open source chord extraction algorithms.
Answer: Well, you can try another set of algorithms for frequency-domain, like wavelets. But I am not sure if that will do for your accuracy issue. Actually, I didn't understand in what way you are having trouble with the FFT. It will always be an approximation of the chord, there is no perfect way to retrieve that kind of information on sound.
So, it depends on the analysis you do on that spectrum, with single notes, there is actually a lot of better algorithms than the FFT, but with chords you will very likely have to work with FFT.
The problem you will have to deal is split the fundamental harmonics from the upper harmonics, one thing that may help is only consider frequencies that are on the guitar range.
If you only have to work with guitar sounds, you should give some time to study the normal frequency-domain graph of the guitar and try to use that to improve you accuracy.
Comment: Hi! When using FFT, is it possible to use the intensities of the bins to try and determine the notes that comprise the chords? Because I think that they will have some type of correlation with each other.
Answer: The FFT can and will give you all the single tones if you set the software up properly.  The whole point of the FFT is to discriminate tones, or if you're an astrophysicist, you want to know the individual elements (sulpher, hydrogen...) that is in the light coming off the star.
Harmonics are not a problem because they have less 'power' than the fundamental frequencey, for example, C=440hz, but C=880hz as well, but 880 will be the smaller spike in the FFT results.
Comment: nope, that is not true, if you try to draw spectrum produced by FFT, for example, for C5 note played on a violin you'll see that C5 has lower amplitude than C6.
Comment: @YuriyKravets I think he means you can find the root note as it will be the one with the greatest 'power' as he puts it
Answer: There is a contest between scientist where people try to analyze different parameters of music. One of section of this contest is chord recognition. This contest is public so anyone can participate in it and show the results in this sphere. The results of the 2011 year is published here.
A friend of mine has achieved good results in this sphere (and in this contest too). You can read about his approach on his webpage.

Guitar Chord Recognition Algorithm?


How to measure ocean vertical velocity?

Question: While horizontal velocities in the ocean are relatively easy to measure, what methods are available to measure vertical velocities? Is there some indirect way to estimate vertical velocities from observations?
Comment: [Neutral-buoyancy floats](http://www-argo.ucsd.edu/Gould_Float_history.pdf) are the most direct method that I know of.
Answer: Direct measurements of three-dimensional ocean currents are carried out with acoustic Doppler current profilers (ADCPs). The ADCPs are usually moored and bottom mounted instead of being ship-based or attached to a floating mooring to minimize the vertical displacement associated with the vertical motions of the ocean surface caused by waves.
The ADCP does not measure horizontal or vertical velocities at a point but determines Doppler shifts along three to five acoustic beams that are typically slanted (most commonly 60°) from the horizontal plane and spaced around the horizontal compass. The most typical configuration (Janus) includes four orthogonal beans. The Doppler shifts measure slant velocities of suspended acoustic backscattering particles moving with the water relative to the instrument. Pairs of slant velocities are combined to produce vertical and horizontal velocities. The underlying assumption is that velocities are horizontally uniform over the beam separation. Other instruments (e.g., Teledyne Sentinel V ADCP) have an integrated fifth beam to provide a third vertical velocity measurement.

Indirect estimates of vertical velocities can be obtain in several ways. The most common approach is to take advantage of the principle of conservation of mass (continuity equation, as described in the answer by Neo).
$$
\dfrac{\partial w}{\partial z} = -\dfrac{\partial u}{\partial x}-\dfrac{\partial v}{\partial y}
$$
where $w$ is the vertical velocity. Assuming $w=0$ at the bottom, then measuring the horizontal velocities throughout the water column will give you an estimate of the vertical velocity. This method, while useful, tend to produce really noisy results as the vertical velocities in the ocean tend to be quite small and are masked by the noise in the horizontal measurements.
A completely different approach was recently introduced by Klein et al. (2009). It uses the surface Quasi-Geostrophic approximation to estimate low-frequency vertical velocities in scales between 20 km and 400 km from the surface down to 500 m. The needed data is some high-resolution Sea Surface Height (SSH, usually from satellites) and an approximation of the large-scale vertical stratification. Vertical velocities are estimated from the buoyancy equations at the surface and at depth in a modified version of the Omega equation (Hoskins et al., 1985).
Comment: +1 but maybe a bit too soon?
Comment: I know. I thought about waiting, but didn't want to forget about the question. It happens when my mind is in too many places...
Comment: +1 Nice answer. If you don't mind, I will add a section to your answer about measuring w with floats in the next few days when I get a chance
Answer: As a non-oceanographer, I might approach this from a continuity standpoint. The sum of the fluxes in each direction must equal 0 (conservation of mass, basically). So you might have some measurements in the x and y directions, which could then give you at least an estimate of the vertical velocities in a given water column, assuming uniform lateral and vertical compositions. There are more assumptions you'd have to make, such as what is a reasonable water column size, that I am not privy too.
While I wouldn't use this in a scientific paper, I'd bet it would be a good enough initial calculation to see if some question is worth doing a more accurate method.
Just an idea... definitely not a definitive answer.
Comment: I was taught this method in physical oceanography courses, and have seen it used in scientific papers. Not sure why someone objected and marked it down.
Comment: @MarkRovetta This is certainly an indirect method that can be used to derive vertical velocity in the ocean. I downvoted because of colloquialism and lack of scientific approach. Also, second sentence is false - conservation of mass, not momentum.
Comment: ie conservation of momentum: my mistake, it cannot be conserved because as the volume changes (through a pipe for example) the velocity increases but the mass does not.

How to measure ocean vertical velocity?


Why does Indy pause while writing "neolithic" in the campus scene?

Question: In the university campus scene in Raiders of the Lost Ark, Indy is writing "NEOLITHIC" on a blackboard. He reaches 'H', but pauses after putting down the two vertical strokes, seemingly confirms something and resumes writing it. What is the meaning of this?
Comment: Do you mean when he checks that he spelled the word correctly? Isn't it just him in his awkward, hesitant professor persona?
Comment: One of the most famous monoliths is Stonehenge, which is several stones standing straight up.  Note how many times he draws a straight line standing on end in a row.
Answer: He's reminding himself how to spell the word.
If you listen, he spells the word to himself, trying to remember the correct letters.

"Neo," meaning "new"
  and "lithic"... L-I-T-H...I-C, meaning "stone."

That's all it is.  A minor gag, just the slightly absent-minded professor of archaeology needing to remember how to spell an archaeological word.


Roman Numeral Analysis: What is a Bb/Db/F chord in the key of C Major?

Question: In the key of C Major what is the Roman numeral for a B ♭/D ♭/F chord that goes to a flat VI?
Comment: You most likely aren't in C major anymore if you are going from Bb minor to Ab major.
Comment: I don't see why the answers assume that the B flat chord in the question is minor.
Comment: @Dekkadeci Because the combination of these three notes is a minor triad. Has the question been altered since your comment? Or possibly your browser isn't showing the flat signs that the OP put after the B and the D?
Answer: Like in any Roman Numeral analysis, minor chords are represented by lower case letters and major chords are represented by upper case letters. In addition if the root is a lowered scale degree you put a flat in front of the scale degree and if the root is a raised scale degree you put a sharp in front of the scale degree.
So making a name for any major/minor chord with Roman Numerals is easy. If you were 100% sure the key is C Major you would have bvii and bVI as seen below.
<code>X:1
L:1/2
M:
K:C
V:2 clef=treble
"bvii"[_B _d f] "bVI"[_A c _e]||
%
</code>
The thing you need to be aware of is the Roman Numeral analysis is a tool that has its uses and its limits . As you get away from functional harmony concepts and ignore other harmonic concepts like secondary dominants and modulation the results aren't as useful as they could be. Even when it makes sense to use chords outside the key in the case of borrowing, too much can signify you need to look at the progression in a different light.
In your case if you were in the key of C, I doubt the you would still be in the key of C seeing the progression Bbm, Ab and if you have an Db next I would argue that you are in the key of Db major instead.
Comment: Possible borrowings from the Phrygian mode, Dom.
Comment: Could be @Patrx2, but without seeing the source I wouldn't assume especially since borrowing vii from Phrygian isn't the most common move. A lot of people like to use Roman Numeral analysis to "hide" functional rather than expose it. I can't tell you how many II7 I've seen instead of V7/V.
Comment: Borrowing from (or shifting to parallel) Phrygian isn't the most common thing, true enough, but when it happens, ♭vii is probably the most common manifestation of it: ♭vii6 pretty much defines the mode.
Comment: More likely to be key of Ab than Eb? And - whatever key it's modulated into will become the 'I', but how does that get notated?
Answer: I agree that it sounds like a modulation. Determine the new key and analyze in terms of the new key and put brackets around all chords relating to the new key. If the new key is Db Maj, then Bb is probably minor and it is vi of Db, the new I, and so on.
Answer: It's bvii, bVI.   It COULD be the beginning of a modulation, maybe to Db major (or several other places).  But it doesn't have to be a modulation.  If the next chord is V, or a climb back up to I, it could just be a touch of colour in C major.
Answer: My Understanding of the 'Roman Numeral Notation' depends on the Scale Degree.
In the Major Scale of 'C', the 1, 4, 5, Are Capitalized. The 2,3 6, are lower case. The 7th, is also lower case, as presented...
I ii, iii,IV,V,vi,vii. in the key of 'C' Major,'d' minor, 'e' minor, F Major, G Major, 'a, minor, 'b, diminished.


Is it possible to install Ubuntu directly from and to the HDD?

Question: I live a long way from stores. I'm in rural Eastern Cape South Africa. I downloaded Ubuntu but I don't have any blank DVD's. Can I copy it to my HDD and install from there?
Comment: Are you already running Linux with grub2?
Answer: You can install from a hard drive, as long as it's not the hard drive you're installing Ubuntu in (you need a spare/external one).
The answers to this questions explain how.
You can also use a flashdrive.
Answer: Well, yes, it's possible. Yet it is quite a bit easier to use a DVD or USB pen drive. So, if you want to have the "simply works" experience you might expect from Ubuntu, try to get a DVD-R or a USB pen drive.
If you are still motivated to try the HDD boot method, read the documentation for the alternate CD, at least the parts about installing from HDD. Since it's a guide for the alternate CD, it might be worth to also download the alternate CD instead of the normal Live-CD, to ensure that everything works as described.


Should I rely on Visual Studio in adding HTML and CSS?

Question: I am wondering if I should rely on Visual Studio in adding HTML and CSS elments by using the viusal toolbars or should I write them by myself? Is it considered bad practice if I relied on Visual Studio to do that?
Answer: The way I usually work when there's a choice between using a tool that will add code for me or writing the code by hand is to use the tool when I'm just starting out but then fairly quickly move onto editing the code directly.
Having moved in to Silverlight in the last couple of years I had to learn a whole new UI language - XAML. So in the first instance I used the visual designer in VS2008/VS2010 and then in Expression Blend to create my first UIs. Once they were created I then went to the text editor to tweak the designs and remove any unnecessary code - usually extra grids.
Now I'm comfortable writing XAML from scratch in the text editor (though having InteliSense and auto-complete helps!), but I use the visual designer when I need to.
The visual tools are a great way to get something on the screen quickly, but you should always double check the code it produces. If nothing else you'll be in a better position to understand why something isn't working as you expect.
Comment: I had the same experience with XAML, although I was frustrated with VS after about 10 minutes and did a split screen.  Edit the XAML and see the change.
Answer: I wouldn't consider this to be bad practice.  You use an IDE to help you write code with higher productivity; therefore you should use its features.
I would recommend that you know how to read and write HTML/CSS if you're a web designer/developer;  that way you won't have to depend on a tool that you may not always have available to you.
Answer: Use it but know it.  In other words, don't just press the "I believe" button on whatever IDE or tool you are working with.  Utilize the Rapid Application Development aspects, but when it comes time to troubleshooting you should be able to read the IDE-generated aspects and go from there.
Knowledge is power, but automation is speed.  The combination of them is even greater than either separately.
Answer: I suppose it depends on the level of control you want... my experience is that slapping something together quickly is usually accomplished by the IDE drag-and-drop tools.
If you've used MVC, you'll know what I'm talking about. It doesn't have designer support, so it forces you to write a layout from scratch. You're not doing it completely blind though, because MVC's pattern is almost a guide to ensuring your view renders neatly.
As others here mention, it's the obvious starting place if you're new to Web Forms. The more you use it, the more you realize that you'll be tweaking minor changes and eventually, you'll be exposed to all the common elements you'll write from scratch one day.
Best of luck.


Removing Fruit From Secondary

Question: I recently brewed a peach hefeweizen and I added 7lb of fresh peaches to the secondary.  I just chunked the peaches and popped them into the carboy.  I have siphoned the beer out for bottling and now I am left with a carboy full of peach chunks!  What's the best way for getting these out?  I was thinking about just soaking them with some PBW and then maybe mashing them up a bit.
Answer: Is your carboy glass or plastic? If you're using a plastic carboy you definitely don't want to go mashing things around inside because you'll run the risk of scratches. Bacteria hide in scratches.
I'd recommend adding some OxyClean or PBW, some hot (not boiling!) water, and shaking up the carboy until the fruit pieces break up into smaller ones that will pour out. Fruit that has been soaking in liquid for a long time is going to be pretty soft and should break up fairly easily.
Comment: I use glass, but that's good advice regarding the scratches in plastic.  I ended up using PBW and soaking it overnight.  It pretty much broke up on its own after that.  I am going to give you the answer because of the scratches comment.
Answer: I found the fruit to be fairly soft already. I used a short, hard plastic stick to help me get them out. Mashing them up a little first might help.
Answer: I've found a bottle/carboy washer (little attachment you can put on your faucet) and a carboy brush to be invaluable in cleanup.

Removing Fruit From Secondary


YA novel: boy and girl adventure in a forest, one ends up moving away

Question: I read a book with a very colorful cover about a boy and a girl who lived near each other and would meet on this hill every day in the summer to adventure through this forest. They make up spirits that guide them and ones that hurt them. The children are pretty young but I remember them touching each other at one point I think. At one point, they fall asleep in a flower bed, and at another, the girl falls into a river. Maybe. At the end, one of the kids moved away which really bummed me out because it seemed like they were going to get married or something. I also think the mother was an alcoholic or a drug addict but the main chunk of this books was these kids adventure in a forest. The book was pretty descriptive and beautifully written.
Comment: Are you certain all of these elements are from the same novel? Because some of it (especially the girl falling into a river) sounds VERY much like the Bridge to Terabithia.
Comment: I am very sure. I have never read Bridge to Terabithia.
Answer: I think the book you are referring to is Bridge to Terabithia.

It's the story of fifth grader Jesse Aarons, who becomes friends with his new neighbor Leslie Burke after he loses a footrace to her at school. She is a smart, talented, outgoing tomboy, and he thinks highly of her. He is an artistic boy who, in the beginning, is fearful, angry, and depressed. After meeting Leslie, his life is transformed. He becomes courageous and learns to let go of his frustration.
Comment: Hopefully people wouldn't give you negatives for that. Was my first guess too.
Comment: No sir, it is not. This book is more poetic almost, and the cover is veryy colorful. It looks sort of like a watercolor pointing.
Comment: Ok my apologies. Is there a way for me to remove my answer so I don't get negatives because I really felt that it was The Bridge to Terabithia.
Answer: It was Too Far by Rich Shapero. I thank you all for your help, anyway. I highly recommend it. It's a great read.

On the outskirts of Fairbanks, six-year-old Robbie meets a mesmerizing girl his own age, and together they explore the mysterious woodland surrounding their homes. The world they discover is built from their fantasies, and inhabited by creatures born from their dreams.
But while Robbie and Fristeen grow inseparable, Robbie's parents are drifting apart, and Fristeen's mother is coming undone. As their homes become increasingly unstable, the children travel deeper and farther into their private world. The forest—and the gods who inhabit it—becomes their refuge until, at summer's end, they are forced to choose between the crushing prospects of the real world, and the lethal demands of their ideal one.


Are there Buddhist traditions without monks?

Question: Are there any traditions without an associated monastic community or even where the monastic element is significantly minimised. I practice with the Triratna Buddhist community and the blurring of the monastic and lay elements is a particular feature. I was wondering if we are very peculiar in that or if there are other traditions, modern or historic, where that also would be the case.
Answer: SGI, for example, describes itself as a "lay Buddhist organization".
I'm not sure I'd want to call it orthodox Buddhist, though.
Traditionally there might have been a split in lifestyle between monastery (and a literate life) and fields (and manual labour). I think I remember seeing a TV documentary with teenagers, monk-candidates, studying texts in a monastery: one said that the (academic) study is difficult/onerous, nervertheless easier (therefore a better career choice) than spending life working in a (agricultural) field.
Answer: Yes, Jōdo Shinshū (Shin Buddhism) has been a lay movement since it was founded in 12th century Japan. The following is from the description on the Facebook page of the North American Shin Buddhist Association.

Total Lay Control
NASBA follows the early Shin Buddhist ideal of total lay control of the sanghas with an egalitarian, non-elitist and democratic format. Originally, Shin Buddhism did not have or need religious professionals like monastics or clergy. Spiritual transmission was not passed down from teacher to student but as Shinran Shonin taught, it unfolds as shinjin (true entrusting mind), which manifests directly from the Primal Vow of Buddha Amida. Inspired by the original intent and teachings of Shin Buddhism, this North American association does not follow any spiritual hierarchical or vertical (top-down) organizational format but adheres to a flat or horizontal design. It does not ordain clergy or have any rituals of guru to student transmission. It believes that all spiritual endowments come directly from the inconceivable Great Compassion, symbolized by the Primal Vow of Amida Buddha.

Lay people can become lay ministers in Shin Buddhism and use the title Reverend.
Answer: Another tradition without monks is Aro:

The Aro teachers are not monks or nuns. They are ordained Tantrikas – whose lives are, in many ways, quite ordinary. They may have conventional jobs, or raise children. Many teach as married couples. Their wisdom is embodied in the ways they live everyday life. Facing the same life challenges as their students, they are able to offer advice that is grounded in personal experience as well as profound religious understanding.

It seems that, like the ones already mentioned, it isn't too orthodox.
Answer: There is a reason that the traditional Buddhist (at least Theravada) orders have Monks and Householders. The monks take the opportunity to practice more intensely  and with a fewer distraction than lay people. Also it is regarded a duty of the householder to support the monks.
Also for the survival of the Dhamma and Practice you need an institution which is the order of monks.
Also in the Theravada perspective when you are enlightened you have to enter the order as a monk hence the order needs to be there. As a householder you cannot survive. E.g. Pukkusati, Bahiya Daruciriya, etc.
Within the bound of Theravada line of thought you cannot have a Buddhist order with no monks.
Comment: I'm not sure whether 'survival' is a requirement: [Thee Days More](http://www.ashidakim.com/zenkoans/25threedaysmore.html) :-)
Comment: The enlightened person can become an anagarika I think, if there is no order.
Comment: "Also in the Theravada perspective when you are enlightened you have to enter the order as a monk...".  ¿What would happen if someone became enlightened and did not "enter the order as a monk"?


Is Tile same as Layer?

Question: Is there difference between a tile server or a layer server?
Can I load tile in ArcGIS control in WPF from some other source?
Can I host my own layer server? Or is there any such thing as layer server?
Comment: As per the [Tour] there should be only one question per question.  Please [edit] this one to focus on whichever one its only answer is addressing so as not to invalidate that.
Answer: I am not positive, but I think you mean dynamic or tiled map services?  The difference here is the speed with which a web application will work.  Tiled services are cached at different levels - meaning a bunch of tiles are created at each level to improve speed.  Dynamic services have no cache levels and take longer to load.  You would need to use a dynamic service if your data is going to be editted often or is going to have its symbology changed.
ESRI documentation on cahcing map services (tiles):
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/What_is_map_caching/005300000059000000/

Is Tile same as Layer?


RSA Signature Weak Padding Attack

Question: Assume that we have a message $m$ of size $n$, and it is padded with two 01 bytes in front. Then  the signature $s$ is computed using a private key $ks$. Can we still use the Known Message Attack to create a signature for message $m^2$ or $pad||m||pad||m$ by multiplying the signature with itself? Or will the padding stop this despite being weak?
Answer: If we note $|m|$ the number of bits in the bytestring coding the message $m$, the first padding considered is $m\mapsto \tilde m=257\cdot2^{|m|}+m$, and the signature is $m\mapsto\tilde S(m)=S(\tilde m)=\tilde m^d\bmod N$, where $S$ is the textbook/naked RSA signing $m\mapsto m^d\bmod N$. Notice that for any $m$ small enough that $m^2$ can be signed, we can derive $S(m^2)$ as $\big(S(m)\big)^2\bmod N$; and if $n^2$ is too big, we may still have $S(m^2\bmod N)=\big(S(m)\big)^2\bmod N$.
NO, we can not derive $\tilde S(m^2)$ as $\big(\tilde S(m)\big)^2\bmod N$. That equality holds if and only if $\tilde m^2\equiv\widetilde{m^2}\pmod N$. At least, when $m$ is small enough that $\widetilde{m^2}<N$ or some similar huge bound (not explicit in the statement), that simplifies to $\tilde m^2=\widetilde{m^2}$, and there is no $m$ matching that: notice that the square of an integer which two leftmost bytes after removing leading zeroes are 0101 has its two leftmost bytes after removing leading zeroes among {0102, 0103, 0104}. I conjecture, without proof, that above said bound, we can not efficiently come up with any solution without knowing the factorization of $N$.
But NO, the scheme is not secure. Even with the (unstated) constraint of messages of the same width, it is easy to come up with distinct messages $m_0, m_1, m_2, m_3$ such that $\widetilde{m_0}\cdot\widetilde{m_1}=\widetilde{m_2}\cdot\widetilde{m_3}$; and then we can derive $\tilde S(m_3)$ as $\Big(\tilde S(m_0)\cdot\tilde S(m_1)\cdot\big(\tilde S(m_2)\big)^{-1}\Big)\bmod N$, where the inverse is computed $\pmod N$.

More generally, linear padding schemes (such as the second one proposed) are weak in RSA, and subject to attacks. See Dan Boneh's Twenty Years of Attacks on the RSA Cryptosystem, section 4.1.
Even non-linear padding schemes may be quite weak; for example (INCITS/)ISO/IEC 9796:1991 (informally known as ISO/IEC 9796-1, and mostly described in section 11.35 of the HAC) was trounced in 1999, then withdrawn.
Using a padding scheme with a hash helps, but is not an insurance of security against such forgeries, even in combination with a linear padding scheme; for example ISO/IEC 9796-2:1997 was shown to have a vulnerability (not practically exploitable in any setup that I know of), even in its strengthened variant of 2002, now officialy designated as ISO/IEC 9796-2 scheme 1 and in wide use, that prescribes a hash of at least 160 bits. However I do not know of any attack (even theoretical) on the padding of RSASSA-PKCS1-v1_5 of PKCS#1.

Conclusion: when at all possible, and in any setup where an adversary could obtain the signature of chosen messages, use RSA signature schemes with provably secure padding based on Full Domain Hash, like RSASSA-PSS of PKCS#1, or when message recovery is needed ISO/IEC 9796-2 schemes 2 or 3 (although I have never seen a complete formal proof of the later ISO/IEC 9796-2 schemes, I trust them enough).
Answer: Considering the padding as an addition, padded message passed to sign is $m\cdot 2^{16}+0101$, $0101$ in hexadecimal, assuming padding is done on the lower bytes (for higher bytes the logic is just the same). Being $e$ the private exponent, and $m^2$ computed in the size of $m$,
$(m\cdot 2^{16}+0101)^e \pmod m$ is very different from $(m^2\cdot 2^{16}+0101)^e\pmod m$, and clearly $(m\cdot 2^{16}+0101)^{2e}\neq(m^2\cdot 2^{16}+0101)^e$.
Comment: When signing, the private exponent _d_ is used, not the public exponent _e_. Also, the definition of the padding is now clarified, and is not as in this answer (please excuse my first comment, which was wrong).

RSA Signature Weak Padding Attack


Calendar overlay colors not shown in Outlook

Question: I created a Sharepoint calendar with several colored overlays.  I click the Connect to Outlook button and the calendar is shown in Microsoft Outlook.  The colors are not shown.  Everything is a uniform color.  Is there any way to show the colors in Outlook?
Answer: Not to my knowledge, the overlays are just useful ways to group data visually.  It all exists in one calendar in SharePoint and therefore it all gets pulled in as one calendar into Outlook.  Outlook calendar overlays are different calendars entirely layered on top of each other.
Comment: was afraid of that :I
Answer: Actually figured it out.  You can use Conditional formatting to set the color of the event.  You will need to make sure that for example the subject contains a certain text that you can search for.


Boundedness of Surfaces in $\mathbb R^3$

Question: GIven an equation such as $ax^2+by^2+cz^2+dxy+exz+fyz=g$ where $a,b,c,d,e,f,g\in \mathbb R$, How can we tell if the surface described is a bounded one without explicitly plotting a graph?
Answer: With $$ g > 0:  $$
It is bounded if and only if $$ a > 0 $$ and $$ 4 ab - d^2 > 0  $$ and $$ 4 abc + def - a f^2 - b e^2 - c d^2 > 0.  $$
This is called Sylvester's Criterion. See also TWEETY. And SYLVESTER.
Comment: Haha! Nice associations...!
Answer: The surface is bounded iff the eigenvalues of the matrix $\begin{pmatrix}
a   & d/2 & e/2 \\
d/2 & b   & f/2 \\
e/2 & f/2 & c \\
\end{pmatrix}$ have the same sign.
One way to show this is to compute the extrema of function $$(x,y,z)\mapsto x^2+y^2+z^2$$ restricted to the surface. You can do this using Lagrange multipliers very easily.
Alternatively, it is not difficult to see that there is a linear change of variables which takes your function to one of the form $$\alpha X^2+\beta Y^2+\gamma Z^2$$ for which the question is very easy.


If I've created a multichain node using params anyone can connect can i change it now?

Question: If I've  created a multichain node using params anyone can connect can i change it now ? i want only few more nodes to be able to connect to my running multichain-node. I want to block malicious notes to be able to connect.
Answer: MultiChain 2.0 beta 2, scheduled for release next week, will allow this. You'll need to first upgrade your blockchain to the latest protocol, and then you can upgrade the anyone-can-connect parameter.


How can I call third party APIs from inside a smart contract at a set time or interval?

Question: In a scenario where a smart contract needs to check against a third party service (Let's say an API with weather information from a trusted source like Weather.com) and make a decision on moving tokens or some such action based on the results for a specific date/time (for example a refund if there is rain during a scheduled cruise) - Can this all be written from within the smart contract and scheduled as well? If so how would you go about calling an API and scheduling when that call would be made?
Answer: I'm not sure but I think that's the purpose of Inbound Oracles to write data on the chain.
You should develop an application that reads data from somewhere and input to your smart contract weather table. And then you can always read from it inside your contracts much faster without spending cpu bandwith...
The problem is that you would need the storage for these weather data.
Comment: Thanks, is there an example somewhere of calling an API from inside a smart contract?
Comment: I don't believe it's possible to call an external API from a smart contract because it may return different values to the different BPs, which would break determinism. I think you need to listen for changes to your smart contract, and provide input to them at that stage. That's kind of what @Leo is saying here I think.


If my professor says "du", can I use "du", too?

Question: Some professors and university personal always address their students with "du". Should I as a student reply with "du"?
If not, how can I  ask them if its okay?
Comment: Das ist keine Sprachfrage, sondern eine Lebenshilfefrage, und hier Off-topic, meiner bescheidenen Ansicht nach.
Comment: "Duuu, Professor, ich hätte da mal ne Frage..." :P imo in research groups Du is common, also as foreign english speaking students often only know *you*. So if he is the Prof. of your research group and says *Du*, why should you use *Sie*?
Comment: Very relevant discussion: [How can a native English speaker know when it is appropriate to use the polite (Sie) or the familiar (Du)?](http://german.stackexchange.com/questions/77/how-can-a-native-english-speaker-know-when-it-is-appropriate-to-use-the-polite-s)
Comment: Since the question linked by @Joachim Sauer has 28 upvotes, I'd suggest that this is also a language question, though a very specizalized version of the other question.
Comment: I get your point and respect your opinion, though I disagree. Maybe this question should have been closed as a duplicate then (IMO best way to tell a reader that there's another question that contains everything you need, even though this is not an exact duplicate); but there's already an answer by Joachim Sauer that is not really in the other question. Anyway. If the community thinks this question is off-topic, it will be closed eventually (we'll know that GL&U is on a good way when closing without mods is done within hours, later within minutes (; ).
Comment: No. The on-topicness of this question can't be proven with the upvotes of a different question - not even by upvotes on its own. b) The other question asks for a general rule. Here we are asked to answer for individual cases. Without detailed knowledge about the relations in question, the question can't be answered, imho.
Answer: In my experience the "asymetric Du" (as I call it) is somewhat of an old concept and is going out of style lately.
Normally the Du/Sie between adults is symmetric, so if your professor says "Du", then so can you.
But traditionally in a hierarchical settings the "higher" person sometimes had the benefit of saying "Du", while the "lower" person was still expected to use "Sie".
From your description it's hard to judge what is expected of you here.
Comment: Agree, I think "asymmetric Du" is today e.g. used by teachers for younger students (i.e. below 16 years), where it is fine (not because of hierarchy, but because of child vs. adult). And it is also sometimes used in a family setting (e.g. the parents of your girl friend say *Du* to you, but you say *Sie* to them until they offer the *Du*). Other than that, adults should be addressed as "Sie" (or, rather, symmetrically, as you call it).
Answer: When I was an apprentice in Swabia it this asymetric Duzen was perfectly normal. The foreman would alway say du and we would siez. That changed when I was finished. You gained the priviledge to be symetrically adressed.
Comment: To be honest, I find this kind of "asymmetrical duzen" quite impolite. I don't know if I would want to make an issue out of it though.
Comment: Interesting. +1 for sharing this experience. In my company, people in probation period (no apprentices) are addressed as "Sie" by one of the bosses. After that, "Du" is used exclusively (also symmetrically, of course).
Comment: Being an electrician appretice has nothing to do with politeness ;-) 20 years on things will have changed a lot though.
Answer: It might depend on the region. Here in Vienna, "du" is always mutual at university, so, yes, you would use "du" on a professor that adresses you with "du". There are some professors who prefer mutual "du" and some who prefer mutual "Sie", but I haven't encountered asymmetric "du" so far (at university), and it would be perceived as odd or impolite by many students.
If you are unsure about the local customs, I would recommend to ask a fellow student that has been around longer than you have, or some other third person, for example, the professor's secretary.
Answer: Using "Sie" is appropriate if you have a formal relationship to the other person, if the other person is older, in a higher position (e.g. your boss). It means you respect the other person.
If a person tells you only the last name you should use "Sie".
(I am a native german speaker and it's much harder for me to insult a person I address formally)
Using "Du" is appropriate if the other person is much younger (you would never say "sie" to a child), if you are friends, or if you are related. You would also use "du" if you want a personal relationship, so if you are speaking with other students or girls (in your privat time, not in office) you are interested in, you should never use "sie".
If a person only tells you the first name, it is the same as offering "du".
(Formerly children were used to adress their parents formally, but that's a long time ago.)
If I were in your situation, I would always use "sie" if I spoke to professors. If it's okay for them if you use "du", they will tell you. As you are not a native speaker it would also be ok if you ask him, but I wouldn't do so with my professors. I'd wait until they offer me to use "du".
Asymmetrical "du" is quite normal if the other person is much older or definitely higher in hirarchy.
"Knigge" is a book which answers many questions to good behaviour with other people. According to them, the person who is higher in hierarchy offers the "du" (source).
If you already used "du" and the professor didn't tell you to use "Sie", you should continue to use "du". If a person askes you to use "Sie" or "du", you should definitely do so.
Some of my personal experiences:
When I was in school in Bavaria, every teacher used "du" and every pupil "sie". Some of my former teachers offered the "du" after I got my final exam, but it were always the younger teachers. Every teacher asked us if it is still okay if they continue using "du" after we attained full age.
While I was doing community service (every German has to do either community service or military service) I used "sie" for all of my co-workers, as I was 20 and all of them were at least 30 and they had much more experience in the work than I had. All of them offered me to use "du" on my first day, except the boss. She was very young, but her position was higher. I guess she didn't offer me "du" as she had to tell me if I did something wrong and it's easier to do this on a formal basis.
I recently experienced that members of different political parties are used to a different behaviour. If you are on a meeting of the SPD it is very likely that they use "du". If you are on a meeting of the CDU it is very likely that they use "Sie".
A friend of mine who has a very good feeling for beeing politely uses "Sie" when she speaks with other students she works with. I was quite surprised as I would never use "Sie" if I spoke to other students in roughly the same age.
Comment: `Asymmetrical "du" is quite normal if the other person is much older or definitely higher in hirarchy.` Unless the younger one is a child, I definitely disagree. Yes, it's in use sometimes, but it's perceived as odd and impolite nowadays, and I wouldn't call it "normal".


(How) Can I hire an instructor as a tourist driver on the Nürburgring without renting a car?

Question: I'd like to take my car on a couple laps around the Green Hell (Nordschleife track). I have no experience as a race driver. I'd rather not crash my car but I don't want to go slowpoke speed either. Actually, I'm a little scared and I want to do this to increase my confidence, so I'd like to get some feedback while driving. The FAQ and various internet sources suggests that hiring an instructor is possible, but I cannot find where and how. (How) Can I hire an (English speaking) instructor without also renting a car?
Comment: Do you mean hire a racing instructor, skilled in racetrack driving, or a normal driving instructor?
Comment: @DJClayworth someone able to help me with tips on how to take certain corners, control my car etc. I already have a drivers license and I am familiar with driving a rally car on 'normal roads'.
Answer: EDIT:
I think what you have exactly in mind is not really possible. Driver instructors which are doing their job for a living need to have insurance and they will lose it if an accident happens and, even worse, could be held responsible for the accident. This is an inacceptable risk.
There are many Motorsport freaks driving on the Nürburgring who probably could give you instructions for free, but this is like lottery and I don't recommend it.
On the other hand, driving your own car is possible, but its called "Green Hell" because of trees (For the people who don't know what that mean: No straw bales, no cushioning if things go wrong). Too many dead people ending up on one, so I do not recommend trying to avoid slowpoke speed.
So either drive in your own car carefully or use an instructor with an insured car. Both are AFAIK not possible. Sorry for the misunderstanding.
The address for getting an instructor is the Drivers's Academy which allow to drive either a sports car or even a fully functional race car. They also explicitly mention support for beginners:
Comment: I still can't seem to find it :(
Comment: It doesn't explicitly state that you can hire an instructor who will take place in your personal car. Also, I doubt that an instructor would join you in your car, of which he has no knowledge regarding roadworthiness. So I would guess that effectively, you hire a car as well in all these offers.
Comment: Ah, that's really too bad. I saw they have a newer version of my car, guess I'll have to live with hiring theirs then, that should be pretty similar. I'll give others some time to write up an answer saying it is possible, otherwise I'll accept yours.


my 2011 Chevy Equinox check engine light on, reads code P0420

Question: Check engine light been on.  I checked gas cap the other day and it stayed on. I will put premium fuel in next time i fill up.  It's been on for about a week.  Any ideas to cause or solution?
Comment: Well, it's a code for poor catalytic converter efficiency, so the first thing to check is if it's still doing it's job.
Comment: how many miles on the car? it may still be up for the federal emissions warranty. My friend just went through this on his 2011.
Answer: P0420 is probably the most common code seen.  It refers to "Catalytic Converter Efficiency"
Basically, it Engine Control Module (ECU) monitors the chemical constituents of the exhaust, both before and after the catalytic converter.  The Catalyst is really a small furnace that reburns the exhaust and adds more oxygen where necessary, to eliminate harmful emissions and convert them into [hopefully] mere carbon dioxide and water.
If the ECU doesn't see the proper changes in the exhaust, eventually it will set the Check Engine Light with a code of P0420.
While being one of the most common codes, it can also be one of the most inaccurate.  Perhaps your catalytic converter is failing, or "poisoned" from chemicals that were not supposed to be in the exhaust. More likely is the the rear oxygen sensor is failing or contaminated, giving false reports to the ECU about the catalyst health. However, unless your 2011 Equinox has a great deal of mileage, I doubt either of these explantions. The code can be cleared for free by a local auto parts store, or you can purchase or borrow a scan tool very inexpensively that will allow you to clear this code.
You can also complete several so-called "drive cycles" GM Example in an attempt to clear the code, but this can be a considerable time and effort sometimes.
You might also purchase one of several "magic juice" solutions at the auto parts store, which can clean and improve, to a limited extent, a tired catalytic converter.  But a long steady highway drive should do the same.
If the Check Engine Light goes away but later returns, further diagnostics will be necssary due to the ubiquitous nature of this code.

Other posters are correct:  if the catalyst needs to be replaced, it
  may be covered under the 8 year / 80,000 mile extended emissions
  warranty.
Comment: I doesn't matter if you clear the code, the problem will not go away, and, depending on the jurisdiction, the car will not pass emissions test if the monitors are not ready. When the code is cleared the car will have to do again the diagnosis of the emissions system which involve driving the car at certain speeds for a certain time (depends on the model/engine). Honestly, this is a great source of confusion. The check engine light was not supposed to turn off while the diagnosis is not ready.
Comment: @Gabriel Diego Not *every* P0420 is a perfectly accurate, irrefutable analysis of catalytic converter health.  Prolonged improper Air/Fuel Ratios can temporarily deplete the Oxygen Storage Capacity in a catalyst, the odd occasional glitch in a drive-cycle monitor, and a host of other things.  I was not suggesting circumventing an emissions jurisdiction, nor was that what the OP asked.  I would not "throw a cat" at a customer car, without first duplicating the CEL, and investigation other running conditions as you succinctly mentioned in your answer.
Comment: I didn't mean to say that you are suggesting that. I just mean that it is frustrating that the check engine light can be tampered so easily to foul people who don't have access to an OBD2 scanner that the car is working perfectly while the problem still is latent and may come back sooner or later. I know many people that told me: "I bought car and the CEL came on after only 15 miles I drove it. I must be so unlucky". I agree that sometimes the CEL is spurious and may go away by itself (or after clearing it).
Answer: There is actually a letter that was sent out (I also have a 2011 Chevy Equinox with this issue and just had my cat. conv. replaced because of it) saying there may be thermal damage or melting on it and if you have this issue to take it to your dealer to get it repaired. Did you get that letter?
Answer: It can be many things
I mean, way many things, as SteveRacer has already cited. The most common (but not unique) is a failing catalytic converter. Please note that often a bad catalytic converter usually is a symptom of a problem, not a cause. If you replace it without solving the source problem, it will fail again in very short time. If this is the case and this came on recently you can try to use a fluid to clean the emissions system to solve this problem, at least for some time to buy you time (or to do smog, if it is required in your jurisdiction). I used Seafoam once and it solved for a few dozen miles.
Using premium fuel will do nothing
Only use the specified fuel grade for your car. Higher octane level in the gas is to prevent it to flashing prematurely in a high compression engine. If your car uses 87 gas and you put 91, you will just be wasting money.
Check if the warranty is still valid for the catalytic converter
In the United States (should be your case, right?), the catalytic converter is warranted by law for 8 years or 80000 miles (whichever first occurs) and if your car is within this warranty it is illegal to remove the catalytic converter yourself. You have to bring to the dealer and they should do it for free. I think that in some states (like California) the warranty is even longer.
Comment: No idea what you mean "the gas may not burn completely due to lower compression"  Have any factual reference information on this?   While I agree you should use a RON rating consistent with the owner's manual, I've *never* seen admonition to not use Premium gasoline.  Poison a cat with oil or coolant, overheat and melt the ceramics by running *lean*, but I sincerely doubt octane or other knock additives (MTBE, ethanol) damage catalysts.  I also do not agree with your assertion that compression has anything to do with complete combustion, *unless* there is a pre-detonation issue.
Comment: Higher octane levels mean higher resilience to spontaneous combustion. That means that to burn a high octane fuel you need an engine that operates at higher compression or the combustion may (or might) not be complete. This does not kills the catalytic converter instantly (or alone) and does not even happens to all cars, so the biggest risk involved actually is to waste money on a more expensive fuel with no return.
Comment: Sorry, I simply do not agree.  Need a good spark, that is all.  Higher octane may be more *friendly* in a high-combustion application, but they do not mandate higher compression.  the retardants resist PRE-detonation, knock, ping -- combustion initiated WITHOUT spark before TDC, that ruins hp and can cause damage.  While I agree higher octane or RON fuel has *less* energy content (BTUs), that doesn't mean it can only be ignited by spark under higher compression. When operating Closed Loop ECU is adjusting air/fuel ratios many times a second.  Only missfires P030x would leave HC in the exhaust.
Comment: I had read an article that this is an hypothetical situation. I will remove it from the answer to avoid misleading.
Comment: Thanks, excellent edit.  +1  If you can find the article, I'd be interested to read it.  And I too agree that unless the ECU actively monitors knock, and can advance timing when using higher octane gasoline, there is no advantage and a huge drain on the wallet.  I use 91 octane in my BMW 2002tii F production race car, because it is cheap, doesn't knock, and has MORE energy content (BTUs/gallon) than 110 octane racing fuel.
Comment: I can't remember where I read it, it was a while ago. You may look for the subject using search engines and you may find some references (most of them apocryphal). Racing fuel often uses alcohol in the composition, which contains less energy per weight and more water concentration. I remember when I was a kid seeing cars operating in ethanol with carburetors (in Brazil) pouring lots of water through the exhaust, almost like a hose.


Public key validation through private key

Question: What is a good way to validate that the public key claimed to belong to a particular user really belongs to him without revealing the associated private key? Can this be done with zero-knowledge proofs? or is there a better approach.
Answer: You can ask them to sign a message. https://github.com/ethereum/wiki/wiki/JavaScript-API#web3ethsign
You can verify the signature with ecrecover in Solidity. Have a look at this answer for examples: ecrecover from Geth and web3.eth.sign
Hope it helps.
Answer: This can be done by Signing and Validating. If someone signs a message with his private key, you can check that the public key belongs to that person by validating the signed message with it.

What is Signing?
Signing is the act of a user A "signing" data that anyone can validate came from user A. This is used in transactions to check if they are real.
[...]
Instead of real-world signatures, which can be faked, the digital ones can not. If you want to know user A did something, make them sign it before moving forward. Then if a dispute arises, check the signature.

You can sign using web3.eth.sign and validate signatures in solidity using ecrecover, as said by Rob Hitchens in this question. This is also explained in depht in the linked blog post.


If all Banks in the world are emptied..?

Question: What would happen if every person in the world pulled their money out of their bank accounts?
Comment: The answer would also depend on whether we're just assuming that all retail consumers are pulling out their money, or whether we're assuming that all deposits from any source are removed. It would further depend on what we assumed people were doing with the money— if they're all holding onto it as cash (assuming that far more cash were created to meet the demand), the effect would be very different from the case where everyone put it in money market funds, for example.
Comment: My answer would depend on how fast they pulled their money out. Could we assume that they did so slowly, say 1% of current balances a week for the next two years? Do you imagine this happening overnight?
Answer: The thing with these economics questions that never happened empirically is always the same: nobody really knows.
Befor Creditanstalt 1931 nobody thought that a bank can go bancrupt, during BrettonWoods/Goldstandard freely floating exchange rates were sought of being detrimental and dumb....
But in theory everything should collapse due to our fractional reserve system that requires banks to have a certain amount of money stored in their books for every granted loan.
But thats not going to happen because centralbanks would intervene and convince people that they are going to do anything to keep the banking system working. If the CB is able to make a trustworthy commitment that should work. Because a rational individual should have no incentive to have so much cash... The costs of carrying so much money are simply too high...
Once there was this Eric Canton attempt....
Comment: My understanding was that many banks went bankrupt before Creditanstalt. See for example the paper Contagion Effects of Three Late
Nineteenth Century British Bank Failures which discusses the failure of Overend Gurney and Co. (1866), City of Glasgow Bank (1878), and Baring Brothers and Co. (1890).
Comment: I have to agree with @Bkay, "nobody thought" is entirely too sweeping - finance is populated with plenty of people who do think about these things and make large sums of money from the people who aren't thinking. They may not talk about it too much afterwards of course. Large scale bank failures were a feature of the 19th century, quite often with failure in one country leading to a cascade failure in others. The Goldsmith banks of the previous century also failed pretty regularly. There is nothing intrinsically stable about banking.
Comment: The point of positing an absurd hypothetical is to respond with an established theory and see what is predicted to happen in the boundary cases. Not an epistemological explanation about the limits of economics knowledge.
Comment: you are certainly right, but the Creditanstalt story is the one you read quite often as being the first.... But the sad thing about the stories is that nobody thinks about them when something bad is about to happen (due to this "this time is different" mentality) - everyone forgot about Creditanstalt when Herstatt was about to collapse. Nobody thought of Herstatt when Lehman was almost down. Of course thats not an accurate statement and a bit exaggerated
Answer: In principle, not that much would necessarily happen: if people pulled out their bank deposits in the form of cash, then the central bank would just become a much bigger financial intermediary.
Cash is a liability of the central bank: when it introduces cash into the economy, it uses that cash to buy an asset. In a world where the public switched to cash en masse, a central bank fulfilling its usual operating procedure by targeting short-term interest rates would fully accommodate that spike in demand for cash by making much more of it, and accumulating assets in the process. What would these assets be? Well, in this situation they would naturally be loans to banks, which would need the funding.
So by withdrawing its funds from the banking system, the public would just trade off holding deposits directly in banks for holding these assets indirectly through the central bank (by holding cash that is backed by loans to those banks).
Of course, this is all a bit idealized. In practice a mass withdrawal of funds would presumably be somewhat chaotic, and the central bank would have to be diligent about its role as lender of last resort to avoid disaster. But there is a natural way for the system to work here, and it's amusing to contemplate how in this scenario, we'd really just be adding one more layer of indirection to the financial system.
Answer: A such systemic bank run would be caused by a massive loss of trust in the banking system and financial markets. Its a collapse and bankrupt of banks possibly capitalism system as we know it. It would be a new era.
New institutions would emerge. Possibly decentralized ones like Bitcoin. If there is no possibility of international payments, international trade would be almost non existent.
How would credit would exist in such a world without money creation and central banks?
Majors big investissements would be difficult.
In fact I don't think people would withdraw money in the first place. In a total loss of confidence money would be worth nothing. Perhaps metals would be back in fashion for trades. Perhaps a cooperative system of reputation like Stackoverflow...
There exist a realistic possibility of collapse. What if a virus enables automatic payment system like interact or cirrus? In an instant destroy the banking system before people could actually withdraw.
In any case I do not forsee a calm transition to a new system. Forget rational behaviors then.


How do I learn what I can do with /proc and /sys

Question: I'd like to know more about the advanced uses of the /proc and /sys virtual filesystems, but I don't know where to begin. Can anyone suggest any good sources to learn from? Also, since I think sys has regular additions, what's the best way to keep my knowledge current when a new kernel is released.
Comment: For the latter, I recommend the kernel mailing list. Failing that, the patch notes.
Answer: You can look into the documentation which comes with the kernel source. (possibly greping for proc/sys ...).
Located at Documentation/filesystems: proc.txt and sysfs.txt.
Answer: Read this blog post: Solving problems with proc
There are a few tips what you can do with the proc filesystem. Among other things, there is a tip how to get back a deleted disk image or how to staying ahead of the OOM killer.
Don't forget to read the comments, there are good tips, too.
Comment: Nice article. BTW, we prefer a small summary/explanation of whatever you link to, beyond just the title. That is, we need to know beforehand what you are asking us to visit.
Comment: I would vote up twice if I could
Answer: The documentation in the Linux source tree is a good place (usually found in /usr/src/linux/Documentation is source is installed). Some distros make a separate package out of it. But, alas, much of it can only be understood by looking at the kernel source code. I have tried to encapsulate some of it in Python modules, so you might also be interested in that. The procps source code is also a good source of information.
Answer: The IBM DeveloperWorks library is a good place for articles like this. I didn't find anything directly applicable, but the 'Resources' section of a paper led me to this.  It has some good info...
http://www.comptechdoc.org/os/linux/howlinuxworks/linux_hlproc.html


2003 mercury ls premium wagon with white smoke coming from hood and rough idle in drive (sputters)...why?

Question: Looking to buy a used 2003 mercury sable ls premium wagon. It only has 97k miles on it but it idles rough in drive while stopped and has white smoke coming from the hood. What could be the issue?
Answer: Don't buy it. Seriously, it could have major problems and there could be many causes, perhaps multiple causes.
White smoke indicates coolant, probably steam from overheating or a coolant leak spraying over a hot engine. It could be cracked radiator, split hose, bad hose connection, or an engine seal.
Rough idle is likely a separate issue, and could have many causes, here's just some of them:

Fuel supply problems: bad filter, bad pump
Injectors failing or clogging
Ignition system issues, bad HT leads, weak coils, bad plugs
Sensor problems: MAF, air temperature, engine temperature, lambda, etc.
Computer malfunctions: the Engine Control Unit (ECU)

There's more on top of that. The problem is you don't know what you're getting, it could be something really cheap and simple; replace the spark plugs and tighten a hose connection and you're good. It could also be expensive and complicated, if you have a blown head gasket it's probably more than the value of the car to fix, unless you can do it yourself and want a project.
Also consider if someone is selling this car with known issues they probably haven't been maintaining it, so there would be many other problems you'll discover later.
Comment: Great answer! ±1