Xenserver 7.3: Changes to the Free Edition - <AUTHOR> https://xenserver.org/blog/entry/xenserver-7-3-changes-to-the-free-edition.html <comment><USER2> What I find interesting is the aversion to paying for what is essential a product mostly used by businesses.

I get the non-profit,school dilemma. and ideally, they do something about that.

but they aren't closing the source of their system ( everything is remaining open source ). They are removing some value add that for the most part, only business users care about. ( to the binaries they provide, are they forced to give you free compile time and bandwidth too? )

For example, I myself have been guilty in previous companies of spending $1M in hardware, and have used the free version of xenserver ( 120 huge vm node deployment, hybrid cloud ), to great success, and Citrix as a company has gotten zero of that.

So here I am, an user extremely happy with software that is being used to run a multi million dollar, profitable business, spending $8-15k per server, and giving zero to the company that made part of this deployment successful.

I gave hundreds of thousands to dell ( and indirectly intel, ram manufacturers, etc ) I gave hundreds of thousands to Arista ( including support and software licenses )

but zero to Citrix, because they gave me such a great free product, i didn't need their support.

License fees have certainly been out of whack with many of these companies ( per socket licensing for example ), but the fact remains, they are providing a business value, and should be compensated. ( and no, ovirt isn't quite there yet, vmware is, but that's even more expensive ).

Not sure what the answer is here, but I do feel that if you are a money making business, buying servers for thousands, a percentage of that should go to the software you use to make those servers useful.

<comment><USER3> >Not sure what the answer is here, but I do feel that if you are a money making business, buying servers for thousands, a percentage of that should go to the software you use to make those servers useful.

Totally respect where you're coming from - but at some point isn't that kind of their problem? It's not your job to monetize it for them.

I respect them making this move, however I think they had better options. Part of their problem is it's _TOUGH_ to go from giving something away to monetizing. At the same time the people like you who were making a profit off of it probably will begrudgingly pay for the upgrade.

I think they should've gone the Redhat route - where they only release source to patches between releases. If you _REALLY_ want to apply the code and build the new binaries yourself, so be it. If you find value in them writing and providing the patches - pay for it.

There is no perfect answer, but I think the people calling for their heads are being a bit silly. I have no doubt the two options were: make this change, or kill the project entirely. ESPECIALLY in the face of Amazon moving away from Xen - I would imagine there was some back-end funding going on there.

<comment><USER2> Oh of course, but I'm a big believer in social contracts. What can I say :)

-

Citrix used to have XCP ( Xen Cloud Platform ), as a way of OSS the core functionality away from the paid functionality. They moved to one build in the possibly naive thought that making licensing a feature of a support contract, would enforce a social contract of "hey, why not pay these guys".

That did not work.

I think AWS moving away from XEN is a bit moot. While AWS did contribute back _some_ to XEN, they mostly forked it for their use case. They are doing the same with KVM. Citrix has been by enlarge, the majority contributor to XEN.

</comment></comment></comment><comment><USER4> This is a major issue - even if the current set of features in the free version are sufficient for a particular project, this action means that we can't rely on long-term goodwill of them staying that way, so any future-proof project should use something that's more free.

<comment><USER5> Precisely. Lacking that goodwill, any potential user would be ill advised to begin using the free version. Current free users would be ill advised to continue with no guarantee of bug & security fixes, because near as I can tell these changes weren't obvious from prior product roadmaps.

</comment></comment><comment><USER5> I don't see a problem with them charging for these features. What I don't like is it appears to have been part of a longer term bait and switch strategy designed to hook users that might otherwise have chosen OSS, with gradual feature removal as the stick used to beat locked in users into paying.

<comment><USER6> It's just as likely that they originally hoped their model would result in enough conversion to paying customers that they could keep funding development but that things didn't work out as they'd expected. I would never assume the 'bait and switch' tactic unless it was a Microsoft or Oracle product.

<comment><USER5> Maybe you haven't had the pleasure of dealing with Citrix as a vendor then, or have been extremely fortunate in that relationship. I myself would grant them no such pass. But I would hesitate to place even Microsoft into the vile sphere of desolation and malice occupied by Oracle, though admitedly my experience with MS has been limited to their bog standard products and licensing.

<comment><USER7> Microsoft can be bad, but I think Oracle is run on pure spite.

According to legend (I wasn't actually there - this is secondhand, so do take with a grain of salt), they tried to convince a company I worked with previously that they needed an additional license for the server that processed backups. No Oracle client or server installed; the logs were pushed via ssh. When they balked, Oracle tried to increase the price two more times. It was apparently great motivation to move to MySQL.

Maybe that was just one particularly bad rep, but I don't think I've gone through a single year of my career without hearing something absurd about them.

<comment><USER5> My story with the big O stems from one of their ERP systems. It got pretty tangled, but here's the 2-minute version:

A contract was signed and during early implementation Oracle EOL'ed a significant module with a replacement that was _planned_ but did not _exist_. Followed by attempts to charge us for their development of the replacement which, again, had been a pre-paid module in their off-the-shelf ERP. Already paid for.

That didn't fly, but later the replacement lacked key features: A web-facing portion collected information. We demo, it works, we ask where data processing folks view it in the forms app... crickets. Conversation ensues:

O: _" It's in the database"_

Me: Sure, but where do users view it when collating the other information?

O: _" Well, a dba can get to it"_

Me: Okay, but when we go live, will it show up as a another tab in a form or...?

O: _" We've completed our build of this feature"_

Me: Hold on, collecting & processing this data is a critical and contractually itemized deliverable. You have developed half of that deliverable.

O: _" We've completed out build of this feature"_

I was probably fortunate that my CIO was there, and took over at that point. A few weeks later, Oracle walked off the job. There had been delays in a modules I wasn't involved with, and Oracle wanted more money. It was a fixed-price contract, and we wouldn't re-open negotiation on a signed contract already multiple milestones in on its payment schedule. Oracle walked. Literally gone, no word, no message, just dozens of people that were there on Tuesday, gone on Wednesday. That's Oracle.

<comment><USER7> Interesting that you mention their ERP systems. One of the projects I'm working with right now has been considering integrating with one, as well. Last week, our CTO put together a big list of pros and cons between the different possible integrations for discussion. The top of the list of cons was "Oracle owns them".

</comment></comment></comment></comment></comment></comment><comment><USER8> If you find yourself impacted by these changes in your home lab (and chances are you will; taking ballooning out of Free is nothing but petty), keep in mind that you can follow the lead of the major hosting companies and jump ship to KVM via oVirt or some homebrew. KVM is better in a number of ways anyway, one of them being a lack of control by Citrix, not to mention when Linode switched they got ~30% more perf out of Linodes.

Xen has been dying for a while. EC2 is heading off it, and they've held out the longest. This change is evidence that Citrix would like to accelerate that trend by killing off the home lab users that stuck it out (read: me). Looks like I have a new Christmas project.

[https://cloudplatform.googleblog.com/2017/01/7-ways-we- harde...](https://cloudplatform.googleblog.com/2017/01/7-ways-we-harden-our- KVM-hypervisor-at-Google-Cloud-security-in-plaintext.html)

[https://www.theregister.co.uk/2017/11/07/aws_writes_new_kvm_...](https://www.theregister.co.uk/2017/11/07/aws_writes_new_kvm_based_hypervisor_to_make_its_cloud_go_faster/)

[https://blog.linode.com/2015/06/16/linode-turns-12-heres- som...](https://blog.linode.com/2015/06/16/linode-turns-12-heres-some-kvm/)

[https://www.digitalocean.com/help/technical/general/](https://www.digitalocean.com/help/technical/general/) (Cmd+F KVM)

<comment><USER9> Which Linux distro do you recommend for running KVM? Additionally, SmartOS has good support for running KVM virtual machines [1]. It gives good solid stability and integration with ZFS, not sure of the performance though vs Linux. The main downside of SmartOS is somewhat sporadic hardware support (broadcom nic's out, intel nic's in). I prefer SmartOS now where I can, but knowing which Linux distro is useful especially for GPU support.

1: [https://www.joyent.com/blog/why-smartos-kvm-dtrace-zones- and...](https://www.joyent.com/blog/why-smartos-kvm-dtrace-zones-and-more)

<comment><USER10> I recently moved my homelab to NixOS, since it lets me use the same system to manage the hosts and the guests declaratively.

I wrote up my approach at [1], in case you're curious.

1: [https://nixos.wiki/wiki/Virtualization_in_NixOS](https://nixos.wiki/wiki/Virtualization_in_NixOS)

<comment><USER9> Interesting approach! When/if you update a KVM instance, does it recreate it?

<comment><USER10> No, the contents of the instances are managed by a separate NixOps network, since it would be wasteful to send the full image (~1GB) for each instance each time a package is updated.

The purpose of the base image is to preinstall something that's ready for NixOps to "take over" with whatever I actually want to run on the VM.

</comment></comment></comment></comment></comment><comment><USER11> For those who want a TL;DR, these are the features that are going to be removed from the free edition:

\- Dynamic Memory Control

\- Xen Storage Motion

\- Active Directory Integration

\- Role Based Access Control

\- High Availability

\- GPU Pass-Through

\- Site Recovery Manager (Disaster Recovery)

\- XenCenter Rolling Pool Upgrade Wizard

\- Maximum Pool Size Restricted To 3 Hosts (existing larger pools will continue to work, but no new host joins will be permitted)

That's quite a list.

<comment><USER3> *from the free edition ISOs that they provide free of charge. The code is still there on github for anyone to build for themselves.

<comment><USER12> Which is not buildable "as is". Cf my other post here.

<comment><USER3> So we've got a company spending millions of dollars developing a piece of software, and then giving away all the source for free. And you think they should be forced to give you documentation on how to build it... why?

I mean, seriously the entitlement is astounding to me. OF COURSE they're going to make it difficult to build on your own, that's part of the monetization strategy. If you don't want to pay for it, and you also don't want to spend the time figuring out how to build it on your own, don't use it. But to act as if they owe you something is... ridiculous.

<comment><USER13> In the first place open source is a set of principals that is designed to inspire people to freely share with one another including the sweat of their brow in the form of direct contribution of work as opposed to cash.

Trying to make that sharing onerous is a violation of those principals and its not entitlement to point this out.

Its a astoundingly stupid monetization strategy. I'm going to assume that building the software may in fact be challenging but its a minuscule fraction of the difficulty of constructing the complete solution.

So imagine it takes 1 person who is paid 120k a year a few weeks to produce a viable solution and documentation. The cost of this solution is about 2k and scales to infinity people.

In a universe where nobody communicates or collaborates I suppose you could imagine that everyone would pay 10k instead of paying 2k in labor for an officially supported solution perhaps in consideration for other value provided like tech support.

The problem is that this fails to consider the fact that someone might actually donate this labor for free to everyone negating the benefit of this particular moat.

It also creates a situation where someone might be inspired to put in the 2k worth of labor and charge 100 users $199 each and come out ahead.

Its certain that a number of players have earned money selling some sort of value add on top of open source software but the value add really needs to be something that you have a competitive advantage at providing not something trivial like a difficult build process.

You are defending nonsense.

<comment><USER3> >Its a astoundingly stupid monetization strategy. I'm going to assume that building the software may in fact be challenging but its a minuscule fraction of the difficulty of constructing the complete solution.

Really? Because that's exactly what Redhat does and they've been continually held up as the shining example of "open source works!" for several decades now...

<comment><USER13> You buy support. Centos exists because building redhat from source isn't hard.

</comment></comment></comment></comment></comment></comment></comment><comment><USER14> Xenserver in my experience at least the free edition is not as polished or stable as ESXi or even regular libvirt/KVM.

I experimented with the 7.2 Free edition and right from the installation not succeeding at first to many other things not working as expected it was not a very good experience. The management client UI is also Windows only I think and it's very sub par.

Given the new changes I wonder anyone would have any reason to run xenserver free edition. There's always ESXi, HyperV and good ole KVM (which maybe an issue if you run Windows server as a VM.)

<comment><USER15> I don't live in the windows world, so I'm curious - why is win on KVM an issue?

<comment><USER14> Windows server is an issue not the client SKUs. Reason is it requires Microsoft signed WHQL drivers so the Red Hat/ Fedora provided ones don't work.

</comment></comment></comment><comment><USER16> David makes an important clarification in the comments:

"I think it's important to differentiate between the pricing of the product from Citrix, and the source code licensing model. XenServer (all editions) remains open source, with the ability for anyone to head over to Github and peruse the code, contribute patches, and so forth. What's changing is what features Citrix puts into the free edition that it builds, tests, and maintains; all of those are still open source, though."

<comment><USER17> What exactly would it mean to exclude features from an edition you provide the source for? Wouldn't anyone just be able to get a copy of the source and build the fully-featured edition anyways? How would these features even migrate - surely you could patch them back in to future version.

<comment><USER16> Right, that's the point. People who want it all for free and don't want to pay citrix anything are free to do so by compiling it from the source. This is 'unsupported' by citrix and you are free to do whatever you want.

The binaries as provided by citrix come in 3 editions. These changes apply to those editions. These are 'supported' by citrix.

<comment><USER18> Ok, but the problem is nobody seems to have the interest in recompiling it for the community (think CentOS).

A few months ago they started charging for patches and someone asked in the XenServer forums here:

[https://discussions.citrix.com/topic/390349-open-source- fork...](https://discussions.citrix.com/topic/390349-open-source-fork-of- xenserver/)

<comment><USER19> When and how (frequently) do the security patches get folded into the source tree?

</comment></comment></comment></comment></comment><comment><USER20> This is very disappointing to hear. I have actually migrated two nodes from proxmox to xenserver + xenorchestra not that long ago. I have no need for a full blown HA environment with dedicated NAS. I didn't have hardware capable of running proxmox on zfs + zfs-sync for a two node setup. Xenserver + xenorchestra (with its continious replication feature for backups) fit the bill much better than proxmox for this use case.

</comment><comment><USER21> Companies that give away core technology for "Free" are always plagued with the perceptive one way door that gets created. There is never a good way out of the situation for either party. The company got the benefit of building a client base with low barrier to entry, but then struggles to maintain profitability after their support/ops burden increases. On the other side, the customer bases profitability and business model was hinged on their ability to innovate to reduce their margins, and now are forced to drastically alter their business plans.

The solution here is for citrix to roll back time, launch a new supported product, and then slowly close the faucet of new features going into the free product. They would have then created an opportunity to pitch the new innovations and migrate their existing customer base to the new platform. The only problem with this thinking (besides the time machine), are the competitors that are releasing more innovative products at the same "free" price point.

Companies, please learn from this: Anything given for free has no value until you try to take it away.

</comment><comment><USER22> I have a project in the planning stages that needs gpu passthrough. What alternative should I use?

<comment><USER23> There are certainly more options, however from personal experience I can attest that ESXi's free license supports GPU pass-through.

<comment><USER24> They generally don't support consumer GPU cards for passthrough however...</comment></comment></comment>


Dropbox remains silent despite more users confirming the email address leak - <AUTHOR> https://forums.dropbox.com/topic.php?id=97303&page=4

<comment><USER2> You cannot prove that Dropbox is responsible for a leak using principals of exclusion. For example, the following is not "proof" that Dropbox leaked your email:

> I received spam at email@example.com, and I have only ever > used this email at Dropbox!

The logic here is that since you only used the specially crafted email at Dropbox, all other possible disclosure sources are excluded. Contrast this to someone having identified a method for accessing user details through some exploit. That would be an inclusive proof. It certainly is cause for suspicion, but it is not proof.

Anyone who has worked in IT for any length of time will tell you that certainty is a dangerous thing when troubleshooting. The more certain you are of something, the less open you are to considering other possibilities. Without fail, the occassion will arrise where that thing you thought was _impossible_ is the thing that caused your problem.</comment>


An Interview With Eric Lippert - <AUTHOR> http://www.i-programmer.info/professional-programmer/i-programmer/7154-c-guru-an-interview-with-eric-lippert.html

<comment><USER2> He has great insights and uses classical analogies to explain ideas. Here is his stackoverflow profile

[http://stackoverflow.com/users/88656/eric- lippert](http://stackoverflow.com/users/88656/eric-lippert)

containing a lot of answers, worth reading even if you are not exactly looking for solution to the problem at hand.

A classic one [http://stackoverflow.com/questions/6441218/can-a-local- varia...](http://stackoverflow.com/questions/6441218/can-a-local-variables- memory-be-accessed-outside-its-scope/6445794#6445794)

</comment><comment><USER3> While C# isn't my favorite language, I always enjoy reading Eric Lippert's measured take on language design. He also has a particularly good sense for how to step back from a question and reframe it in an insightful way, which makes him a good interviewee.

<comment><USER4> Well, C# basically followed the footsteps of Java. Nothing too novel about that.

</comment></comment><comment><USER5> > What will the feature set of C# 6.0 be?

> I am under NDA and cannot discuss it in details ... Incidentally, I knew > Wesner slightly in the 1990s. Among his many claims to fame is _he invented > the pivot table_. Interesting guy.

I.e. _HINT HINT_ (just don't ask me what he's hinting)

<comment><USER6> I don't usually see my name mentioned on the Internet, but I did not invent PivotTables. I essentially was the only full-time developer of PivotTables in Excel 97, and after that release, about 50% of the PivotTable code was written by me.

</comment></comment><comment><USER7> I love the way Eric cheerfully ignores the practical aspects of thawing and freezing cooks while explaining by analogy the difference between asynchronous and parallel processing. I wish I could do that as flawlessly as he can.

</comment><comment><USER8> Is there a reason why you linked to your blog, and not the full interview at the original source?

[http://www.i-programmer.info/professional- programmer/i-progr...](http://www.i-programmer.info/professional- programmer/i-programmer/7154-c-guru-an-interview-with-eric-lippert.html)

<comment><USER9> It seems like the poster is a spammer. All his posts are texts copied from other sources.

<comment><USER10> We banned the site and changed the link. Thanks wslh and dgritsko.

<comment><USER11> but in the very beginning it states "Here we host an overall summary of the highlights of the interview ranging over topics as diverse as the future of C#, asynchronous v parallel, Visual Basic and more (the link to the full interview on i-programmer can be found at the end of this page)". How can this be considered spam ????????????? I think that the notion was to read the highlights and if you find it interesting and want to see more then follow the link to the whole interview

<comment><USER9> Do you ever see a site like this that was not a spammer? I don't think too many people will click in the link the whole interview.

<comment><USER11> if that is so, then you must consider this one as the exception to the rule since that's the PR manager of O'Reilly UK not just 'someone'....

<comment><USER9> _...since that 's the PR manager of O'Reilly UK not just 'someone'_

If she was my mother I would do the same.

<comment><USER11> it wasn't meant in that to treat her in a 'special way', but that being the PR manager of O'Reilly for the whole of UK proves that she is NOT a spammer and that she should not be treated as one

<comment><USER9> You can see blackhat tactics everywhere. Please take a look at the "Reddit Bans The Atlantic, Businessweek In Anti-Spam Crusade": [http://www.forbes.com/sites/jeffbercovici/2012/06/13/reddit-...](http://www.forbes.com/sites/jeffbercovici/2012/06/13/reddit- bans-the-atlantic-businessweek-in-anti-spam-crusade/)

I love The Atlantic but they were engaged in these blackhat tactics.</comment></comment></comment></comment></comment></comment></comment></comment></comment>


The First Image Ever of a Hydrogen Atom's Orbital Structure - <AUTHOR> http://io9.com/the-first-image-ever-of-a-hydrogen-atoms-orbital-struc-509684901?utm_content=buffer7af87&utm_source=buffer&utm_medium=twitter&utm_campaign=Buffer <comment><USER2> This is awesome. I wonder how long it will be before this technique shows us something we don't already know.

<comment><USER3> Might be a while. This looks sort of "crude" and I think it would take big deviation from theory to get people to take such a result seriously. But we won't know without "looking" ... this is a serious awesome look as you note. Putting on my chemist's cap, it's nice to see loose, but still probably worthwhile experimental confirmation of what I learned.</comment></comment>


Local-First Software (2019) - <AUTHOR> https://www.inkandswitch.com/local-first.html <comment><USER2> This was submitted just a couple days ago and didn't get noticed. Good to see it made the front page today.

I think the article drifts a bit far from "Local-First Software" but I learned a lot about the issues dealing with real time collaboration.

I'm just about ready to release a new version of a web app I first released in 2002 that offers a Local-First option. That's been a goal of mine since I first released it. indexedDB works, but that's a pretty awful option for the app I'm speaking of.

I'm using CouchDB to do this, and it requires the user install CouchDB on their desktop PC. That's a pretty big hurdle, but it's actually very easy to do. I think the hard part will be convincing users it's worth their effort.

<comment><USER3> Why not use PouchDB and have that sync up with your main CouchDB server? It seemed like a very powerful paradigm to me, so I am always curious why it did not catch on.

<comment><USER4> There's also RxDB which builds on top of PouchDb: it has a graphql plugin so you can have real-time data as well. I'm using it experimentally with Hasura+Postgres. The only drawback is that I can't figure out a UI that indicates which documents are saved offline for a user.

</comment></comment></comment><comment><USER5> The problem with "local" (where local is maybe not even where you are, but where your base is) storage of data is that it's a pain in the butt. Maintaining hardware, doing backups, etc is fun for me as a hobbyist but is a drag for people who don't like that thing. Cloud took off because it's easy, not because it's better.

</comment><comment><USER6> Fyi... the keyword "CRDT" appears 50 times in the article.

Some past HN threads mentioning CRDT did not fare as well as OT (Operational Transform):

[https://news.ycombinator.com/item?id=19886883](https://news.ycombinator.com/item?id=19886883)

[https://news.ycombinator.com/item?id=19847622](https://news.ycombinator.com/item?id=19847622)

<comment><USER7> Because CRDTs are one of Martin Kleppmann's group main research interests (and a key mechanism in achieving local-first applications that synchronize seamlessly).

Just a few weeks ago he released a video that explains CRDTs in a bit more detail:

[https://news.ycombinator.com/item?id=23802208](https://news.ycombinator.com/item?id=23802208)

<comment><USER8> Yea sure, CRDTs interesting and all, but what if it mentioned blackchain 50 times? Research groups often worship a particular technology for some imaginary practical applications. Take something like collaborative editing, It's "straightforward" to have a people edit a local document and then use a server as the central point of authority, but that is not an open academic question so people want to do it without the central server. Marijn Haverbeke has made this point more eleganty [1].

[1] [https://marijnhaverbeke.nl/blog/collaborative- editing.html](https://marijnhaverbeke.nl/blog/collaborative-editing.html)</comment></comment></comment>


How to not fear your death: An Epicurean perspective - <AUTHOR> https://psyche.co/guides/how-to-use-philosophy-to-overcome-the-fear-of-your-own-death <comment><USER2> I don't really fear dying, I also don't fear being dead.

But the fact that I won't be anymore, FOREVER: that is what literally gives me the chills everytime I think about it.

God, I really hope there's something after death.

<comment><USER3> _> God, I really hope there's something after death._

There is something, it's the same thing that was before your birth, in that sense so you are very much just returning to your natural state: You have been not born for the longest time and you will be dead for the longest time.

In that context this rather short experience of existence is actually the thing that's out of the ordinary, making it that much more valuable.

<comment><USER2> That's exactly what makes it scary to me.

It feels so normal to sit there on my couch, writing this message from my smartphone.

But in fact life is just a ridiculously short period at the scale of... Of what, actually?

How long have I not been born, and how long will I be dead? Trying to make sense of it is what makes me anxious.

<comment><USER4> Yeah, reading about events on cosmological scale (galaxy, blackhole formation, etc.) usually ends up in existential dread feeling for me.

<comment><USER3> I guess it's a matter of perspective.

When I look at these things I'm amazed that I'm part of these scales, or as Carl Sagan put it: "We are made of star stuff".

Once I'm dead, the elements my body consists of will go back into that eternal cycle, making me once again a part of the whole or maybe even part of evolving into something completely new.

While my non-corporeal parts, my consciousness, my character, will hopefully be fondly remembered by family and friends.

At least that's how I found a bit of peace of mind after having suffered from anxiety and existential dread for most of my youth.

</comment></comment></comment></comment></comment><comment><USER5> Maybe I'm wrong, but I don't think most people fear the state of being dead, which is what this essay is centered around. "Fear of death" is more commonly the fear of the approach of the end of life, ranging from the prolonged downward slide into decrepitude or terminal illness on one end of the spectrum to the physically violent moments of struggle against death on the other end.

In other words, if you were 100% guaranteed to die by instant vaporization at some random time in the last quarter of life with no forewarning, would you still fear death?

<comment><USER4> Yes, I would. Thinking about that I will cease to exist sometime is most terrifying.

<comment><USER6> To me it's more terrifying to think that I might loose my mind to dementia or alzheimer's, that I might not know who i am, who i was, who my children are.. that's terrifying. Though I think this experience is even worse for the others. My grandmother had alzheimers and in the last stage she was serene and smiling..

<comment><USER7> If your mind is gone, are you still you? Unless you believe that each human has a unique soul, there's not much left to make you _you_ except your mind. And after a disease has attacked your mind, you might as well already be dead physically because you are a completely different person.

<comment><USER8> Does that matter? If you poke that person, won't they still hurt regardless of who they are?

<comment><USER7> That seems irrelevant. I didn't say they weren't _a_ person, I said it seems unlikely they're the _same_ person.

You seem to be trying to ascribe some sort of ill intent or meaning to my question when there was none.

<comment><USER8> No ill intent ascribed. What I mean is that it'd still be an immense suffering regardless of whether you'd still be you or not.

<comment><USER6> Yes but if it's not you anymore you can't connect empathically with the future you who doesn't know who they are anymore. It's a relief in a way but also scary at the same time.

I've seen a guy in his early 40s afflicted with earl onset dementia and alzheimer and he was loosing it little by little every day and it was terrifying. At some point he stopped knowing who he was and he seemed peaceful. He also could not communicate, care for himself, I don't think he couldn't even feel pain anymore.

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER9> As a counterpoint: [https://www.youtube.com/watch?v=qX6NztnPU-4](https://www.youtube.com/watch?v=qX6NztnPU-4) where 97 year old philosopher who held similar logical views as OP has a change of heart.

Key quote: "In my arrogance, I thought that I could conquer death with logic. But now I know that I only used logic to suppress my fear of death."

What is horrifying to me that his was the best case scenario - lucid at 97.

<comment><USER10> Is it really a best case scenario, lucid at 97?

How bad is it, being non-lucid for the person experiencing it, vs being lucid, when it's time to face your existence?

</comment></comment><comment><USER11> Fearing death oft-times seems similar to the fear that accompanies any act which you've never done before. About to be married, going to finish school, going on a trip... fear is part of all of these experiences, at least until you've done it. But I think the fear is made worse because of the stories we've told, and heard, about it. Modern movies are a prime example where we can watch what might happen if we die and what we might miss, etc. The more tragic a story the greater the fear that that might overwhelm us. The poems, tales, and stories highlight the effects of death.

But in a similar vein, I find comfort in the more positive stories too, such as the ones about Jesus in the Bible. How death came as a result of sin, and how, for some reason, a sacrifice was required to pay the penalty of sin - something else had to die in your stead, like a pigeon or sheep. But of course, how could that really pay that price? No wonder sacrifices were needed regularly. That is until Jesus' death - an eternal life could pay for an eternal death, for good and forever. All I need to do is believe in Jesus and share that payment. This is a good story, preferable to the ending of say, 300, or Gladiator, for me at least.

I'm not sure the eternal life to come will eventually be boring either. The story suggests we remain basically the same, and what has been true is that we grow. True, what interested me as a kid doesn't hold the same power over me now, nor could I as a child really get into fonts or NLP or traveling! So I reckon that eternal life means eternally growing and developing. I can't picture it, I've not lived it yet, there is some fear there, but overall it sounds pretty good.

<comment><USER12> > I'm not sure the eternal life to come will eventually be boring either.

Along these lines, the ending of "The Last Battle" by CS Lewis which ends the Chronicles of Narnia is so beautiful:

"There was a real railway accident," said Aslan softly. "Your father and mother and all of you are—as you used to call it in the Shadow-Lands—dead. The term is over: the holidays have begun. The dream is ended: this is the morning."

And as He spoke He no longer looked to them like a lion; but the things that began to happen after that were so great and beautiful that I cannot write them. And for us this is the end of all the stories, and we can most truly say that they all lived happily ever after. But for them it was only the beginning of the real story. All their life in this world and all their adventures in Narnia had only been the cover and the title page: now at last they were beginning Chapter One of the Great Story, which no one on earth has read: which goes on for ever: in which every chapter is better than the one before.

</comment></comment><comment><USER13> I like this way of thinking of it...Mark Twain quote: "I do not fear death. I had been dead for billions and billions of years before I was born, and had not suffered the slightest inconvenience from it." Of course you can argue that it could be different after, but still.

</comment><comment><USER14> I fear death a lot and it sort of ties in to my weird concept of memory.

If we take the idea of consciousness as experienced by the mind as it functions in the present moment, the past does not exist at all. It has never existed.

This concept of mind is separate to the biological realities of memories in the brain, it's the unknown bit that transforms the grey goo into me.

I have been annihilated an infinite amount of times since I started writing this message. I have only lived because of my memory of the past presents I experienced.

By which I mean the sensation of being alive and having lived is intimately tied up with memory. For past events I don't remember I was effectively dead. I only lived my life because I'm able to live all of it currently.

Rather than life being a column of infinitely small slices of time building up they're all occurring in the present moment. While I'm lying in bed writing this I'm also at school, at swim classes, on work experience, at university, at my first job interview, etc because they are events I know to have happened and experienced because I don't just replay them, in order for my brain to have knowledge of them they're happening concurrently. If I don't remember these did they ever actually happen? From my perspective of the person I currently consider to be me?

What happens after a catastrophic brain injury or during a disease like Alzheimers? I don't think this makes any life worth less but from the perspective of current you it doesn't take the end of life for the death of your current 'life', the impression of an unbroken chain of having lived that forms you, in the snapshot of the present. During temporary short term memory loss do you effectively die?

I know it all sounds very confused but the nature of memory, existence and death freaks me out.

As a counterpoint during Alzheimers a patient will experience bursts of lucidity so obviously there's a solid state backup of the past, distinct from the present, but I get positively vertiginous thinking it over.

</comment><comment><USER15> I was always told as a child "Don't waste energy worrying about things you cannot change when there's so many things in life that energy could be better invested in." Death is coming, but if I waste energy worrying about it, that's energy I could have spent on _living_.

</comment><comment><USER16> Epicurus is great. He represents a very life-affirming and to modesty animating philosophy. Unfortunately he was defamed by all the Christian moral philosophers. This is hinted at in the article.

</comment><comment><USER17> Having been pretty close to dying several times already; what I do know is that once you're there, once you realize it's out of your hands, there is no fear.

The ego is all about self preservation, survival, which is probably a big part of how we got this far.

</comment><comment><USER18> For me it all fits in that famous Rutger Hauer's monologue: "All those moments will be lost in time, like tears in rain" \- still freaks the hell out of me every time. Not that I think of my experiences as especially important, I mean I certainly had never seen C-beams glitter in the dark, but still the idea of all the stories and people I knew in a way dying with me, it just seems like such a horrible waste...

</comment><comment><USER19> I appreciate Alan Watts' perspective, loosely summarized as:

eons passed before you were born...

you'll live maybe a handful of decades...

... and eons will pass after you're gone.

Most people aren't freaked out by the "before", so why not take a similar attitude towards the "after"?

This only relates to existential dread per se (vs eg entirely rational concern for the well-being of your surviving dependents, for example), but I like it.

<comment><USER20> > _Most people aren 't freaked out by the "before", so why not take a similar > attitude towards the "after"?_

Because unlike the before the after means the permanent loss of current, living experience.

</comment></comment><comment><USER21> Something that film critic Roger Ebert wrote a few years before his death has stuck with me:

"I know it is coming, and I do not fear it, because I believe there is nothing on the other side of death to fear. I hope to be spared as much pain as possible on the approach path. I was perfectly content before I was born, and I think of death as the same state."

Assuming that whatever comes after death will be a lot like whatever came before we were born helped me deal with my own anxiety around the inevitability of death. If one assumes these two states are equivalent, then we've already experienced death, or at least a death-like state. Whether that's something to be feared or not is up to the individual, and is a separate question.

Source- [https://www.rogerebert.com/roger-ebert/go-gentle-into- that-g...](https://www.rogerebert.com/roger-ebert/go-gentle-into-that-good- night)

</comment><comment><USER22> The universe existed for 14 billion years before you were born, and it's likely going to exist for some way huger number of years after you die. I expect both experiences (before life and after death) to be the same.

Death does seem scary. But having to live for quintillions of years would certainly be worse.

<comment><USER23> > Death does seem scary. But having to live for quintillions of years would > certainly be worse.

You have no evidence from which to argue that as a certainty. Let's gather such evidence; you could always make a more informed decision at a _much_ later time.

</comment></comment><comment><USER24> I'm excited to see if something happens after death, human bodies are just a cloud of atoms, after all.

<comment><USER6> Something happens, you cease to exist. You won't notice anything

<comment><USER25> You say that with such confidence, yet at one point you did not exist, and now you do. Who's to say we won't one day exist again in some form?

<comment><USER26> That's what gets me. It's nothing forever? It was nothing forever once but one day "I" woke up in the universe.

Leads me to another point. What are the odds of waking up? I think it's with 100% certainty that you become conscious.

Your memories are 100% physical though so that definitely evaporates. Perhaps if you find consciousness again it's as if you awoke from a dream you cannot remember, a new blank slate. You flash forward to the next time you find consciousness.

<comment><USER8> > What are the odds of waking up? I think it's with 100% certainty that you > become conscious.

I'm not sure what you mean here, can you explain what you mean by "you"? What remains to be "you" if your atoms are spread out (happens in life too), your memories are gone and your consciousness is also temporarily gone? Isn't it more like just random parts of the universe coming to life and turning into _someone_? In what way could it be "you"?

<comment><USER25> I think if you were to believe in becoming someone or something once again, then yes, like your memories, your consciousness would be gone. I think this because I think your consciousness is inherently tied to how you sense the universe and your own being, and that will obviously be different if you once again exist as someone or something else.

As a result, if you choose to believe you will one day exist again after you die, in order to make a connection between one or more consciousnesses or lives, you would need to invent something to explain it. Like a soul.

You could make thinking about all this even more wild by thinking about how time is involved in all of this. We are assuming if that you exist again it must be some time after you cease to exist. What if you exist "again," but at the same time you exist now? Are you also another person somewhere else? Is there another universe with another you? When you die do you then relive the same existence again? The questions are as limitless as our imaginations because we have no answers.

<comment><USER8> I'm not sure the last questions could be answered without determining more about this new kind of soul, which by the way reminds me of Locke's substances. A substance for Locke is like an object with no properties whatsoever, it's that which bears all the properties that we observe but which maintains its identity through space and time. I guess we'd need something like that to be 'us' before we're reanimated. The problem though is that none of that is really observable by 'us' being it or anyone living since it really has no characteristics. Doesn't mean it's not real, but not that helpful after all :/

<comment><USER25> Thanks for mentioning Locke's substances. It sounds like quite an intriguing idea. I have not read nearly as much philosophy as I would like, and that gives me a great indication of where to look when I pursue reading more of it.

<comment><USER8> Sure thing, I've just been thinking about object identity recently and they come up quite often. Tthe article in SEP can help you avoid the arcane English of his writings btw.

1\. [https://plato.stanford.edu/entries/substance/](https://plato.stanford.edu/entries/substance/)

</comment></comment></comment></comment></comment></comment></comment></comment></comment><comment><USER27> I'm looking forward to all that life-extension research that's happening right now. Reading all those research papers, it feels as if we're on the verge of being able to actually rejuvenate people for real. We've never came this close to uncovering the underlying mechanics of aging.

So, anyway, hopefully, in the near future, dying won't be compulsory.

</comment><comment><USER28> Self preservation expressed through fear. Can a movie be enjoyed if told that the film is broken and will end abruptly? Without resolution? Life takes one chair away and death stops the music. We all try to find a seat but there not enough chairs. What a game!

</comment><comment><USER29> TLDR: don't fear death because you won't know you're dead.

Pretty much misses the point when the fear of death is frequently not about what comes after, and much more about the big "nothingness" thing.

<comment><USER25> I think that is the whole point. Why fear the big nothingness if it's not possible to experience it? Just like how it's impossible to experience or remember anything before you became alive.

I find it comforting to realize that I once wasn't and now I am. I will once again cease to be. We often think death is final, but if we already made the transition from not being to being, who's to say that, in some form, we might once again become something from "nothing."

</comment></comment><comment><USER30> If you're like me and deeply fear death, and you're curious about how others seemingly ignore the subject entirely, you may be interested in this study posted on HN a while back.[1][2]

[1]: [https://www.sciencedirect.com/science/article/abs/pii/S10538...](https://www.sciencedirect.com/science/article/abs/pii/S1053811919306688)

[2]: [https://sci- hub.tw/https://www.sciencedirect.com/science/art...](https://sci- hub.tw/https://www.sciencedirect.com/science/article/abs/pii/S1053811919306688)

</comment><comment><USER31> I've been reading Seneca's Letters to Lucilious. He says

> For we are mistaken when we look forward to death; the major portion of > death has already passed. Whatever years be behind us are in death's hands.

I suppose I also meditate on christ's suffering. It seems to say that while the end is never pretty for the one who is enduring it, it is intrinsically meaningful and sacred.

</comment><comment><USER32> More to the point - if you accept strong verificationism, statements are only meaningful to the extent they constrain expectations as to future experiences. "I will die" does not, because being dead is not an experience. It's a meaningless statement. It's silly to be afraid of a literally incoherent "possibility".

<comment><USER33> > being dead is not an experience

But getting there certainly can be. "I will die" is not the same as "I will be dead".

<comment><USER32> Sure, but the reaction to that should be different - one should focus on access to painkillers and such rather than some kind of incoherent existential dread.

</comment></comment></comment><comment><USER34> A collection of philosophical thoughts that I should probably put into an essay at some point, but in the meantime...

Some have likened the experience of death to what it's like when you black out (true loss of consciousness) or, to a lesser extent, when you go to sleep at night. One moment you're there, the next moment you're coming back from not being there. (Give me some leeway on the sleep thing - I know that when you're actively dreaming or tossing and turning it's not quite a jump cut).

So in that moment when you're coming back to consciousness from a state of previous unconsciousness, what's to say you're the same "you" that was beforehand? Sure, you remember a whole life, but then there's this gap in continuity. Maybe you were someone else and then all of a sudden, you're now "you" with all those memories in that mushy brain of yours.

But if that's the case, why is the gap of consciousness needed to separate "you"? What's to say that from any given instant to any other given instant the "you" is continuous, other than for this stream of memories coming from your meat brain. Maybe "you" jumps around all the time.

But then - what is "you" anyway? If we're just a collection of meat brain memories, maybe there's no core identifying "you" in the first place, and we're all just part of a big collective pool? Like a piece of code running in an overall shared memory space. The complexity forms (your program / you), and then the function exits and the memory goes back to the collective pool.

So then - what if life and existence is all about perspective? I'm me because, well, I'm me. I expeierience this life and remember these memories. And you're you because you experience your life and remember your memories. Is there really a difference from a third-party observer?

Maybe life is simply in the eye of the beholder. As long as there is ANY conscious life, then life is being experienced. And so maybe death really is nothing to worry about -- you'll get a chance to experience another life as someone else.

But then - why does it even need to be linear? Maybe we ARE experiencing life as someone else -- as evidenced by all the someone elses experiencing life right now :). Just because we can't experience it (hardware limitations - sorry. Brain can't handle multiple sets of inputs ;) doesn't mean it's not happening.

Maybe we're all experiencing consciousness in our own ways as part of one big system. That leopard in the zoo is experiencing it. I'm experiencing it. You reading this are experiencing it. Maybe our meat brains and linear single- track memories are just a nice little lie, and we're really just all temporary functions running as part of a bigger computing system. Function runs, exits, memory goes back to the shared pool. New function runs, exits, memory goes back to the shared pool. Many functions run simultaneously - each doing only what it was programmed to do, then each exits and the memory gets released again....

This really gets wild when you start thinking about clone experiments (or teleportation). Make a perfect clone of yourself right now, down to the neuron, and assemble it in across the room. You'll experience nothing other than to see a clone appear 10 feet away from you. Your clone will have the experience of being you one instant, and then waking up across the room looking at you "Holy cow! Cloning and teleportation worked! They're real!" Then your clone will go on with life, doing the same things you want to do, remembering the same things you remember.

Then think about whether there's REALLY any difference between that clone of you and any other person on earth....

<comment><USER25> I've had a lot of thoughts similar to yours. I especially wonder about the linear qualities we often attribute to life and death, and potentially rebirth. We often assume that if we are somehow reborn, it will be in the future. But what if I am reborn while I still exist, just somewhere else? After all, time is simply another dimension, right? At least, as we humans understand it.

Your comparison to computing, functions, and shared memory is very good at describing that. But to go even further, since computers as we know them still run in a linear fashion with regards to time (forward), what if all consciousness across all time and space is just one "thing?"

<comment><USER34> I love this. And it adds a whole new dimension (ha ha) to the thinking.

And you're right - it starts to get really wild when you remove the linear constraint. Or even the singular universe constraint. Think about a multiverse, where not only are there other people in this one timeline experiencing things, maybe there are multiple (infinite) simultaneous timelines. Or, as you said, not even timelines. Multiple infinite states of being.

I think perhaps the most comforting part of trying to "figure it all out" is the realization that we're, in all likelihood, woefully incapable of really ever figuring it all out, especially if "reality" (whatever that is) looks nothing like the tiny, single-brained, single-universed, linear timeline perspective that we have.

<comment><USER25> Woefully incapable indeed. But at the same time, the inability to know or understand the entire nature of our universe creates an eternal, enchanting mystery, and drives our search for meaning in life. I find it romantic.

</comment></comment></comment></comment><comment><USER35> In an infinite universe you will repeat exactly an infinite number of times. You will repeat with any possible variation even more times. -From physicist Brian Greenes multiverse book.

</comment><comment><USER36> In articles like this, everyone crawls out of the woodwork to brag about how they don't fear death. I don't believe it for a minute. The number of people who could have a loaded gun staring them in the face and truly not feel the slightest bit of fear has to be minuscule. Humans just wouldn't have made it this far otherwise.

What I think is scarier than the concept of non-existence though is the possibility that our universe might be cyclical; i.e., that its evolution would repeat over and over again an infinite number of times. Imagine all of the suffering that you've ever experienced happening again, indefinitely. Or the Holocaust repeating. Or slavery. Just thinking about the idea of an endless, cyclical universe is almost sickening. I much prefer the other theories of how the universe might end.

<comment><USER37> Death is really the only thing I fear. I can't imagine not fearing it. I also don't understand people who say things like "I wouldn't want to live to <500, 1000, some big number>

</comment></comment><comment><USER38> Death is indeed nothing and is nothing to fear. The dread of having minutes, or seconds left to die in suffering on the other hand, is not very pleasant.

</comment><comment><USER39> I'm just gonna leave these here and see if anyone has relevant experiences to share:

> _"There is something about the core of this experience that opens people up > to the great mystery of what it is that we don't know."_

[https://www.scientificamerican.com/article/psilocybin-a- jour...](https://www.scientificamerican.com/article/psilocybin-a-journey- beyond-the-fear-of-death/)

> _"Of the participants who received the high dose in the second study, 83% > reported feeling significantly less depression and 58% reported less anxiety > after 7 weeks. Only 14% of those who received niacin reported less anxiety > and less depression."_

[https://www.sciencemag.org/news/2016/12/hallucinogenic- drugs...](https://www.sciencemag.org/news/2016/12/hallucinogenic-drugs-help- cancer-patients-deal-their-fear-death)

</comment><comment><USER40> > Not death itself, but only the moral preparation for it holds terrors ~ > Aleksandr Solzhenitsyn

</comment><comment><USER41> A perspective: You don't want to be old and regret wasting time worrying about death.

</comment><comment><USER42> Im not scared of death per se. but this is still a unique perspective

</comment><comment><USER43> I'm not afraid of death because I'm a solipsist. But you should be afraid of my death, because when I die all of you will disappear!

That joke and singing along to Monty Python's Bright Side of Life is usually enough to snap me out of the occasional melancholy resulting from contemplating the inevitable.

Ok, but seriously, yeah, I'm terrified.

</comment><comment><USER44> Why not just live in denial like the rest of us?

</comment><comment><USER45> I wish people were more afraid of death. Maybe we'd be doing more about it. Why are we trying so much harder to overcome the fear of death and not death?

> No doubt you don't fear your prenatal existence and logically speaking, > given their equivalence, it follows that you should fear death the exact > same amount, as in not at all.

Prenatal existence is not symmetrical to death, in my opinion. First off, even if they were, neither can be conceived, which makes the symmetry unknowable. But more importantly I don't fear things that have happened, I fear things that are impending - a pretty key distinction here, which I feel fundamentally breaks the symmetry (ie: time is not symmetrical).

> doesn't seem to be the sort of thing that one can reasonably be fearful of > because it isn't anything.

Earlier it was described as the greatest deprivation. Of course that's something. This is like saying "why fear starvation? It is only the absence of something - food". It is the absence, the nothingness, that drives that very fear.

This is like saying "Why fear loneliness? It is not something that is done to you, it is only the absence of love".

Perhaps death is 'nothing', whatever that means. Why is 'nothing' a special 'thing' that I can not fear? It seems just as reasonable to fear 'nothing' as anything else.

IDK, I don't find any of it compelling. Fix death please, that's a good way to prevent the fear.

<comment><USER46> me: "ug, I think I got the group permissions right but not sure why that user still can't read it. So irritating. I'll sort it out but, ug, maybe it's not so bad to procrastinate a bit on hackernews. "

hackernews: "here's some more reasons to fear death"

me: man chgrp

<comment><USER47> Bounce the login session first or test after "bash --login"

</comment></comment></comment><comment><USER48> 99.9999% of people in this thread who say "I fear death" are lying: they are afraid only in the intellectual sense.

How many of those do actually experience the fear of death so deep in their bones that they actually live life to their fullest?

(I'm not claiming I'm one of those).

<comment><USER49> Why is failure to "actually live life to their fullest" evidence that such people don't fear death?

<comment><USER50> What does that even mean? Death is the great equalizer anyway.

</comment></comment></comment><comment><USER51> This should be required reading for doomers.

<comment><USER52> Yeah let's take away depressed people's fear of death, that ought to end well!</comment></comment>


The history of UTF-8 as told by Rob Pike - <AUTHOR> http://doc.cat-v.org/bell_labs/utf-8_history <comment><USER2> <http://news.ycombinator.com/item?id=2071529>

</comment><comment><USER3> <http://news.ycombinator.com/item?id=577116>

I wonder why the dup checker didn't find it - the link is exactly the same.</comment>


Seven Puzzles You Think You Must Not Have Heard Correctly (2006) [pdf] - <AUTHOR> https://www.math.dartmouth.edu/~pw/solutions.pdf <comment><USER2> _Love in Kleptopia_ needs to be explained better. The problem can only be solved if you can afix two padlocks onto a box, and I was presuming the lock box had a single, normally shaped padlock eye, which would make such a thing impossible.

I find this happens a lot with "thought" problems: I can't solve it (and can often prove that) because the rules of the problem are inadequately explained.

<comment><USER3> Reminds me of this: 1, 2, 3, 4, 5, 6, 7, 8, 9,... What comes next?

10 if it's the sequence of natural numbers

13 if it's the sequence of N such that N=2^n for natural numbers n, where N does not contain a 0

153 if it's sequence of N such that the the sum of the digits of N each raised to the power of the number of digits in N equals N.

<comment><USER4> While I fully agree with the premise that any sequence of numbers can have an essentially infinite choice of 'next number', depending on how you define your sequence, and the simplest way to prove that is simply to given a sequence of _n_ numbers solve the _n+1_ polynomial equation, given that it is incompletely specified then you have an infinite number of solutions. Or just drop in a heavy side step function ([https://en.wikipedia.org/wiki/Heaviside_step_function](https://en.wikipedia.org/wiki/Heaviside_step_function)).

However, i'm not sure that I understand your second example.

If N=2^n (assuming 2 to the power of n, not 2 xor n) then one would expect the sequence to be 1, 2, 4, 8, 16, etc.

If N=2^n using the C xor notation, then we would expect a sequence 3, 0, 1, 6, 7, 4, etc

Your third example is pure evil, and I'm glad that I never had you as a maths teacher ;-)

<comment><USER5> It's the sequence of n such that 2^n doesn't contain the digit 0. This excludes 10 (1024), 11 (2048), and 12 (4096). See [http://oeis.org/A007377](http://oeis.org/A007377)

</comment></comment></comment></comment><comment><USER6> In the Dot-town suicides, say the stranger says "Alice has a blue dot." Alice then kills herself. Why would the other residents die?

I think this satisfies the requirements: there's certainly some number of blue dots for which the statement would be false, namely zero.

<comment><USER7> Yeah, I was thinking about if the stranger said something like, "not all the dots are blue." This is non-trivial by the definition given, and no one would have to kill themselves at all.

<comment><USER8> "not all the dots are blue" \- in the case where there are n people with n-1 blue dots and 1 red dot, the person with the red dot kills themself, and then everyone else kills themselves because they know that the red dot person killed themself because they did not see any red dots.

<comment><USER7> Right, but if there were two red dots the town is fine.

In a one red dot town, you could say "there is at least one blue dot"

<comment><USER9> Would they be fine?

So let's say there are two people with red dots, let's name them Ruth and Rudy. Ruth now knows that "not all dots are blue" (which is equivalent to "there is at least one red dot"). She sees Rudy with the red dot: Fine, here's the person with the red dot.

But wait a minute, why is Rudy not killing himself? If Rudy is the only person with a red dot, he should have seen only blue dots... however he knows there has to be at least one red dot, so if he only saw blue dots, the red dot must have been him, so he would have killed himself.

But he didn't, so that means he has seen at least one red dot, which isn't him, and isn't anybody else Ruth has seen because she only saw blue dots otherwise.

Oh no, it must be Ruth with the second red dot!

<comment><USER7> Ok now it is making sense. The same would be true if you went to three dots.... the third person would think, "wait, why aren't the two blue dotted people killing themselves? There must be a third blue dot... wait, the third blue dot must be me"

That makes sense. What about the other commenter, who said something like "Alice has a blue dot."

Wouldn't that not lead to everyone's death?

<comment><USER10> In your three dots logic, this would have a red dot person kill themselves if there are two blue dots: The two blue dotted people aren't killing themselves because they are still thinking "wait, why isn't he killing himself" about the other.

I feel like some timing procedures need to be defined.

<comment><USER7> I think the 'they meet every night' is supposed to be the 'timing procedure'

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER11> Another very counterintuitive (for me) problem:

 _how do you do better that break even in the following game: 'A' chooses two distinct integers, writes them on slips of paper and holds one out in each hand in a fist. You choose a hand and reveal a number. You must then guess whether the other number is higher or lower than the revealed one, winning $1 if you guess right and losing $1 otherwise._

<comment><USER12> After writing this one out, this reminds me of the Monty Hall problem. In this case my guess is that you use a prior -- assume the two unknown numbers are A & B, and then assume a random integer yourself C.

From there, if A (the first revealed number) is less than C, then that narrows the remaining cases giving you a 2/3 chance. If A is greater than C, that also narrows the remaining cases and gives you a 2/3 chance as well.

On a number line, the cases are below.

If A > C then the six originally equally possible cases are narrowed to three cases:

A-----B-----C (impossible)

A-----C-----B (impossible)

B-----A-----C (impossible)

B-----C-----A B < A

C-----A-----B B > A

C-----B-----A B < A

So you would guess B < A -- the first hand's number is higher with probability 2/3.

If A < C then the six originally equally possible cases are also narrowed to three cases:

A-----B-----C B > A

A-----C-----B B > A

B-----A-----C B < A

B-----C-----A (impossible)

C-----A-----B (impossible)

C-----B-----A (impossible)

So you would guess B > A -- the first hand's number is lower with probability 2/3.

<comment><USER13> This works, but you don't get a probability of 2/3, because the cases aren't equally likely. There isn't a probability distribution for C such that for any A and B the probability of A<C<B is 1/3\. We would have to have P(0<C<10)=1/3 and P(10<C<20)=1/3 and P(0<C<20)=1/3, which is impossible.

<comment><USER14> Why does this work with probability 2/3 then?

[https://jsfiddle.net/q4qbewp1/](https://jsfiddle.net/q4qbewp1/)

<comment><USER13> Because of the particular distributions that you happen to have chosen. Alice doesn't have to pick uniformly at random. Since 0^p=0 and 1^p=1 we can experiment with different distributions by using "Math.pow(Math.random(),p)" in place of "Math.random()". For example:

      var prior = Math.pow(Math.random(),1);
      var hand1 = Math.pow(Math.random(),10);
      var hand2 = Math.pow(Math.random(),10);
      > Win probability: 0.5757182

and

      var prior = Math.pow(Math.random(),1);
      var hand1 = Math.pow(Math.random(),0.1);
      var hand2 = Math.pow(Math.random(),10);
      > Win probability: 0.9026432

But the win probability will always be >0.5 so long as the "prior" probability distribution has a nonzero probability of being between Alice's two numbers.

<comment><USER15> > the win probability will always be >0.5 so long as the "prior" probability > distribution has a nonzero probability of being between Alice's two numbers.

Wow. This is the key piece of information that makes the problem interesting, IMO. That's quite unintuitive.

If you know _anything at all_ about how your opponent chooses numbers, you win in the long term.

<comment><USER16> It also tells us what Alice's optimal strategy is: pick the first number at random, and then select an adjacent integer as the second number. Thus, there's no space between them that your prior can assign any probability to.

<comment><USER13> Well your strategy has to have some way of breaking ties, when Alice's number is the same as yours. Lets say that you always say "higher" in that case. Then you always win whenever your number is between Alice's or equal to the smaller of them. Equivalently you could just pick a random half-integer.

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER17> I think there's an easier to visualize solution to the box problem.

Let A have dimensions (a,b,c) and let B have dimensions (x,y,z). Assume A fits inside B.

We have (a+b+c)^2 = a^2 + b^2 + c^2 + 2ab + 2ac + 2bc. This is the sum of the A's hypotenuse squared plus its surface area. The same holds for B.

Note that A's hypotenuse is at most that of B-- the hypotenuse of a is its longest axis, and it needs to fit in B somehow. Further, note that the surface area of A is less than that of B. To see this, consider the nesting of A inside B and realize that both boxes' interiors are convex sets. Imagine inflating A inside of B by taking the sets A_t consisting of all points within B that are within distance t of a point in A. It is not hard to see that this inflating operation can only increase the surface area of A, and since the maximum surface area we can get is that of B we have that A has smaller surface area than that of B. Thus,

(a+b+c)^2 = (A hypotenuse)^2 + (A surface area) <= (B hypotenuse)^2 + (B surface area) = (x+y+z)^2. The claim follows.

</comment><comment><USER18> I loved this. Some comments. Not really spoilers I hope...

For "Unwanted Expansion" the answer is technically correct but I am displeased that it doesn't prove there wont be any infinite loops. Whereas analyzing invariant in the tree should prove that.

For Boxes in Boxes it says "But, if we take ε to be huge", but how big is huge, and what if it isn't huge? Seems like something in the proof is being hand waved over.

The natives and suicides I enjoyed they really made me go aah!. The irony about the suicides is that the if the people were too dumb to apply the logic, they'd survive.

<comment><USER19> "If we take ε to be huge" just means "let's analyze the growth rate as ε goes to infinity". More formally, what's going on is that you have a function which is polynomial in ε and which is always positive; therefore the leading coefficient must be positive, as if it were negative, the polynomial would be eventually negative.

The question "what if it isn't huge" makes no sense; we can pick ε, it's not some external given. (Actually, as mentioned, we're not picking it to be one specific value but rather letting it tend to infinity, but that's another matter.)

<comment><USER18> Thanks. Nice explanation. It's been a while (18 years) since I've read maths proofs.

</comment></comment></comment><comment><USER20> Problem 7 has an even more fiendish counterpart: [https://en.wikipedia.org/wiki/The_Hardest_Logic_Puzzle_Ever](https://en.wikipedia.org/wiki/The_Hardest_Logic_Puzzle_Ever).

<comment><USER18> To make it more fiendish, what if the gods / natives don't know about each other's TRUE/FALSE/RANDOM status (but they are excellent logicians, so they can intuit any information from answers to your previous questions).

</comment></comment><comment><USER19> The "boxes in boxes" problem actually turns out to be true in much greater generality, using a different solution: [https://math.stackexchange.com/questions/1909085/suppose- a-b...](https://math.stackexchange.com/questions/1909085/suppose-a-box-a-is- contained-in-a-box-b-is-the-total-volume-of-the-k-faces-of-a)

</comment><comment><USER21> I always liked the prisoner box question, but I prefer the phrasing where the prisoners are assigned a number and the boxes are numbered. I feel like the "prisoners have to come up with a name to number mapping" step just gets in the way of the interesting part.

<comment><USER22> I don't understand one assertion that the author makes in the solution, though:

        If it happens that the permutation has no cycles of
        length greater than 50, this process will work every
        time and the prisoners will be spared.

Obviously that's not true as written, because the first prisoner has odds of 50% no matter what function or algorithm they use to choose the boxes they open. If they fail in their initial guesses, the game stops immediately and everyone dies. What am I missing?

Furthermore, if you simplify the case to two prisoners and two boxes, where each is allowed to open one box, the odds of "success" are clearly only 25%. What happens as the number of prisoners and boxes grows that _improves_ the odds? This isn't a classic Monty Hall variation where the participants have additional options as the game progresses -- it's completely predetermined.

<comment><USER23> If it has cycles of 50 or less only, then they're guaranteed to find their own name (they start the cycle on the box corresponding to themselves, so that cycle must contain them). Incidentally, the "first prisoner" might as well be every prisoner, because they aren't allowed to observe each other, communicate, or modify the room.

<comment><USER22> _If it has cycles of 50 or less only, then they 're guaranteed to find their own name (they start the cycle on the box corresponding to themselves, so that cycle must contain them)_

But there are 100 boxes, assigned at random. The prisoners can come up with a mapping function that predetermines which boxes they will open based on their names, but that function will have no relationship to the one (if any) that was used by the warden.

There is no way to guarantee that the first prisoner finds his name, and that seems to be true for all of the others. It must genuinely be a case where I haven't understood the problem correctly.

<comment><USER24> If no cycle is longer than 50 boxes (~30% chance of that being true), then by starting with the box that matches your number, you have a 100% chance of navigating to the box containing your number before your 50-box limit is reached. It's impossible to start in the wrong cycle, because that cycle contains neither the pointer or the value.

You have to find your pointer in a circular linked list. But it's only singly- linked, so you start just in front of it and work around the links the long way. 30% of the time, all the lists are 50 elements or shorter, meaning everyone is guaranteed to succeed.

<comment><USER22> But what if your name is in box #51, which you aren't allowed to open?

<comment><USER25> Then there's a cycle of length > 50 and everyone loses.

</comment></comment></comment></comment></comment></comment></comment><comment><USER26> Previous discussion: [https://news.ycombinator.com/item?id=12380879](https://news.ycombinator.com/item?id=12380879)

Some additional fun ones in the comments there.

</comment><comment><USER27> Where can I find more of these?

Do you guys recommend this author's books such as [https://www.amazon.com/Mathematical-Puzzles-Connoisseurs- Pet...](https://www.amazon.com/Mathematical-Puzzles-Connoisseurs-Peter- Winkler/dp/1568812019#reader_1568812019) ?

(It's hard to find the right search term for this that doesn't return a lot of non-mathematical brainteasers or stuff aimed at kids)

<comment><USER28> Winkler's book looks pretty good, yes.

You'd probably also enjoy the works of Martin Gardner, who wrote a recreational mathematics column in Scientific American for 25 years, which has been collected across many volumes.

</comment></comment><comment><USER29> Awesome post! I kind of want to find more of these types of things (solutions to seemingly complex questions). If anyone has recommendations would love to hear

<comment><USER30> I read quite a bit of books of that kind when I was young. I didn't read in English, but "One hundred thousand whys" \- maths in Chinese was a great one, and this [1] in Vietnamese is a great one. They are all old books and some have solutions we can figure out by using a computer, but in general, they are really cool.

My personal favorite that has an English translation available, although it's not on Maths is "Physics for entertainment" by Perelman -- you can get it on Amazon right now. It was published 100+ years ago and problems are still relevant now. It discussed questions such as "When you jump out of a train, should you jump forward or backward?" "Who is wetter, a person standing in the rain or a person running in the rain?"

I guess basic maths and science hasn't changed that much, or maybe I was reading them when I was young, so I might not have known any better.

1: [http://khoia0.com/PDF-Files/80-BAI-TOAN-THONG- MINH_handuc_v2...](http://khoia0.com/PDF-Files/80-BAI-TOAN-THONG- MINH_handuc_v2.pdf)

</comment></comment><comment><USER31> The worst question of the bunch is undoubtedly the tennis question. A very clever alien could answer the other six, but having never been exposed to the rules of tennis would be hopeless against the Wimbledon question.

(In fact my knowledge of tennis is poor enough that I don't understand why the question would be considered difficult for somebody who played tennis.)

</comment><comment><USER32> Spent quite a while on the Wimbledon problem before giving up and reading the answer. But the answer is wrong, because they don't play tiebreakers at Wimbledon (or any of the grand slams besides the US Open). Pretty frustrating TBH. Kind of felt the same about the padlocked boxes one too, although at least that one is more just a little ambiguous vs outright wrong.

<comment><USER33> They don't play tiebreakers in the fifth set. All other sets work normally. The answer is correct because it's only talking about the first three sets.

<comment><USER34> Yeah, but it's so easy! Why is that considered a hard problem? Just because most people are unfamiliar with tiebreakers in tennis?

</comment></comment></comment><comment><USER35> Honestly I already lost interest after reading the solution to the first problem, because there's no indication that the prisoners are allowed to alter the boxes in advance. This is such a dumb "gotcha".

Edit: I re-read the solution and it doesn't require actual labeling (It's hard to imagine, because I'm not a native English speaker).

<comment><USER36> What are you talking about? They don't alter the boxes in any way, they just say "hey, I'm number 1, you're number 2, etc...".

<comment><USER35> you're right, thanks for pointing it out.

</comment></comment></comment><comment><USER37> The Dot Town Suicides appears to be incorrect as stated.

Suppose there are 100 residents and 2 blue dots. The stranger tells everyone "there are not 98 blue dots"

This meets the condition of the question's "non-trivial" but the residents can relax: nobody has learned anything new. The proposed induction is broken, in my opinion.

<comment><USER38> I thought this initially as well: if there are many of each colour, and the only information is that there is at least one blue dot, how could this be new information to trigger the suicides?

But this isn't correct. Let's say n = 6, a-c are blue, d-f are red, and the information is that there is at least one blue dot. a knows there are at least two, but thinks b may believe there is only one blue dot. Moreover, a believes b may believe that c may believe that there are no blue dots.

So if a was red, the information would mean that b would commit suicide if c did not initially commit suicide, but since neither has happened, a must have a blue dot and therefore must commit suicide.

A convoluted process to be sure but does it make sense how the information transmits by ruling out hypotheticals?

</comment></comment><comment><USER39> Likely posted because problem #1 was recently on the front page:

[https://news.ycombinator.com/item?id=16984815](https://news.ycombinator.com/item?id=16984815)

</comment><comment><USER40> The nice thing about this is that we can use Dot-town as a halting oracle, which can then be used to solve any specific undecidable problem we'd want to solve. Make the machine output a set of dots after running some unknown computation, such as a search for twin primes. The residents will kill themselves depending on the results.

<comment><USER41> How so?

<comment><USER42> For a proposition P, make your statement of the form "there are N blue dots iff P".

</comment></comment></comment><comment><USER43> I would love to watch/hear someone go about solving these problems, just to see their approach and thought patterns.

</comment><comment><USER44> " _Communicating badly and then acting smug when you 're misunderstood is not cleverness._"

[https://www.xkcd.com/169/](https://www.xkcd.com/169/)

I've stopped trying to do puzzles. I've been misled by bad communication (intentional or otherwise) too many times.

</comment><comment><USER45> As to the dots, I enjoyed this variation from xkcd, where I first encountered it: [https://xkcd.com/blue_eyes.html](https://xkcd.com/blue_eyes.html)

It massively improved our play at Hanabi: [https://boardgamegeek.com/boardgame/98778/hanabi](https://boardgamegeek.com/boardgame/98778/hanabi)

Probably would be a useful puzzle for improving your Spades or Bridge game, or any game you play with a partner with limited information.

Also, it gets much worse than The Random Native. George Boolos has a variation called "the hardest logic puzzle ever." It goes like this:

"Three gods A, B, and C are called, in some order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer all questions in their own language in which the words for 'yes' and 'no' are 'da' and 'ja', in some order. You do not know which word means which."

There's an ongoing effort out there to make this variation even harder: [https://arxiv.org/abs/1206.1926](https://arxiv.org/abs/1206.1926)

</comment><comment><USER46> I found the "trick" solution to Unwanted Expansion to be unsatisfying: unless I am mistaken, it assumes that all of the values must be positive integers, which was not stated as being the case.

<comment><USER47> no, it's about the structure of the expression expanding indefinitely. if that happened then if all the values were positive then the value of the expression would also tend to infinity

<comment><USER46> Ah, thank you for clearing up my misconception! That makes a lot more sense.</comment></comment></comment>