inter process communication with message passing the shared memory is in
operating system
1344657
Inter-process communication In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categorized as clients and servers, where the client requests data and the server responds to client requests. Many applications are both clients and servers, as commonly seen in distributed computing. Methods for doing IPC are divided into categories which vary based on software requirements, such as performance and modularity requirements, and system circumstances, such as network bandwidth and latency. IPC is very important to the design process
Inter-process communication
267128
with each other, usually by sending messages. Shared memory is strictly speaking also an inter-process communication mechanism, but the abbreviation IPC usually only refers to message passing, and it is the latter that is particularly relevant to microkernels. IPC allows the operating system to be built from a number of small programs called servers, which are used by other programs on the system, invoked via IPC. Most or all support for peripheral hardware is handled in this fashion, with servers for device drivers, network protocol stacks, file systems, graphics, etc. IPC can be synchronous or asynchronous. Asynchronous IPC is analogous
Microkernel
3477147
waiting for events while yielding control to the kernel between each event invocation. Contiki supports per-process optional preemptive multithreading, inter-process communication using message passing through events, as well as an optional graphical user interface (GUI) subsystem with either direct graphic support for locally connected terminals or networked virtual display with Virtual Network Computing (VNC) or over Telnet. A full installation of Contiki includes the following features: The Contiki operating system is ported to the following systems: Contiki Contiki is an operating system for networked, memory-constrained systems with a focus on low-power wireless Internet of Things devices. Extant uses for Contiki
Contiki
12348536
acts as a scheduler for tasks running on the system, providing pre-emptive multitasking with prioritized round-robin scheduling. Exec also provides access to other libraries and high-level inter-process communication via message passing. Other comparable microkernels have had performance problems because of the need to copy messages between address spaces. Since the Amiga has only one address space, Exec message passing is quite efficient. AmigaDOS provides the disk operating system portion of the AmigaOS. This includes file systems, file and directory manipulation, the command-line interface, file redirection, console windows, and so on. Its interfaces offer facilities such as command redirection, piping, scripting
AmigaOS
927463
build efficient virtual machines – see Popek and Goldberg virtualization requirements. With enough privileges, processes can request the kernel to map part of another process's memory space to its own, as is the case for debuggers. Programs can also request shared memory regions with other processes, although other techniques are also available to allow inter-process communication. The most common way of implementing a user mode separate from kernel mode involves operating system protection rings. Another approach taken in experimental operating systems is to have a single address space for all software, and rely on the programming language's virtual machine to
User space
14849543
MQX MQX RTOS is a real-time operating system developed by Precise Software Technologies Inc., and currently sold by Synopsys, Embedded Access Inc, and Freescale. MQX is an abbreviation standing for "Message Queue eXecutive". Like most real-time operating systems, MQX RTOS includes a multitasking kernel with pre-emptive scheduling and fast interrupt response, extensive inter-process communication and synchronization facilities, and a file system. Its configurable size conserves memory space taking as little as 6 KB of ROM, including its kernel, interrupts, semaphores, queues and a memory manager. MQX RTOS includes a TCP/IP stack (RTCS), embedded MS-DOS file system (MFS), USB Host/Device Stack,
MQX
1344657
Inter-process communication In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categorized as clients and servers, where the client requests data and the server responds to client requests. Many applications are both clients and servers, as commonly seen in distributed computing. Methods for doing IPC are divided into categories which vary based on software requirements, such as performance and modularity requirements, and system circumstances, such as network bandwidth and latency. IPC is very important to the design process
Inter-process communication
7300257
HelenOS HelenOS is an operating system based on a multiserver microkernel design. The source code of HelenOS is published under a BSD License. The microkernel handles multitasking, memory management and inter-process communication. It also provides kernel-based threads and supports symmetric multiprocessing. Typical to microkernel design, file systems, networking, device drivers and graphical user interface are isolated from each other into a collection of user space components that communicate via a message bus. Each process (called "task") can contain several threads (preemptively scheduled by the kernel) which, in turn, can contain several fibers scheduled cooperatively in user space. Device and file-system
HelenOS
1344659
are messaging and information systems that utilize IPC mechanisms, but don't implement IPC themselves: The following are platform or programming language-specific APIs: The following are platform or programming language specific-APIs that use IPC, but do not themselves implement it: Inter-process communication In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categorized as clients and servers, where the client requests data and the server responds to client requests. Many applications are both clients and servers, as commonly seen in
Inter-process communication
4395680
other processes with message passing being the preferred form of interprocess communication (IPC), although shared memory was also implemented. MERT also sported a custom filesystem with special support for large, contiguous, statically sized files, as used in real-time database applications. The design of MERT was influenced by Dijkstra's THE, Hansen's Monitor and IBM's CP-67. The MERT operating system was a four-layer design, in decreasing order of protection: The standard supervisor was MERT/UNIX, a Unix emulator with an extended system call interface and shell that enabled the use of MERT's custom IPC mechanisms, although an RSX-11 emulator also existed. One interesting
Multi-Environment Real-Time
5492210
7 or 9. Actor model implementation In computer science, Actor model implementation concerns implementation issues for the Actor model. The Caltech Cosmic Cube was developed by Chuck Seitz "et al." at Caltech providing architectural support for Actor systems. A significant difference between the Cosmic Cube and most other parallel processors is that this multiple instruction multiple-data machine uses message passing instead of shared variables for communication between concurrent processes. This computational model is reflected in the hardware structure and operating system, and is also the explicit message passing communication seen by the programmer. According to Seitz [1985]: The J–Machine was
Actor model implementation
5492206
Actor model implementation In computer science, Actor model implementation concerns implementation issues for the Actor model. The Caltech Cosmic Cube was developed by Chuck Seitz "et al." at Caltech providing architectural support for Actor systems. A significant difference between the Cosmic Cube and most other parallel processors is that this multiple instruction multiple-data machine uses message passing instead of shared variables for communication between concurrent processes. This computational model is reflected in the hardware structure and operating system, and is also the explicit message passing communication seen by the programmer. According to Seitz [1985]: The J–Machine was developed by Bill
Actor model implementation
267119
with the lack of generality and reusability of the RC 4000 system. They feared that each installation would require a different operating system so they started to investigate novel and more general ways of creating software for the RC 4000. In 1969, their effort resulted in the completion of the RC 4000 Multiprogramming System. Its nucleus provided inter-process communication based on message-passing for up to 23 unprivileged processes, out of which 8 at a time were protected from one another. It further implemented scheduling of time slices of programs executed in parallel, initiation and control of program execution at the
Microkernel
10005100
research focuses on microkernels and microkernel-based systems as well as virtual machines, with a specific emphasis on performance and reliability. His group produced the Mungi single address space operating system, aimed at clusters of 64-bit computers, and implementations of the L4 microkernel with very fast inter-process communication. His Gelato@UNSW team was a founding member of the Gelato Federation, and focused on performance and scalability of Linux on Itanium. They established theoretical and practical performance limits of message-passing IPC on Itanium. Since joining NICTA at its creation in 2002, his research shifted away from high-end computing platforms towards embedded systems, with
Gernot Heiser
2014550
computer for its day (Amiga used 25 DMA channels and a coprocessor), Sassenrath decided to create a preemptive multitasking operating system within a microkernel design. This was a novel approach for 1983 when other personal computer operating systems were single tasking such as MS-DOS (1981) and the Macintosh (1984). The Amiga multitasking kernel was also one of the first to implement a microkernel OS methodology based on a real-time message passing (inter-process communication) core known as Exec (for executive) with dynamically loaded libraries and devices as optional modules around the core. This design gave the Amiga OS a great extensibility
Carl Sassenrath
8588529
servers can use the normal thread-level synchronization primitives. Doors can be used to synchronize access to shared memory segments, allowing single-copy data transfer. The Doors concept is very similar to X/Open XATMI API specification, where client processes invoke server processes' exposed functions. In clients, tpcall() is an analogue of door_call() and, in server processes, tpreturn() is an analogue of door_return(). Doors (computing) Doors is an inter-process communication facility for Unix computer systems. They provide a form of procedure call. Doors were developed by Sun Microsystems as a core part of the Spring operating system, then added to Solaris in version
Doors (computing)
7942128
Infiniband. The VxWorks implementation also supports shared memory which can be accessed by multiple instances of the operating system, running simultaneously on the same hardware. Security must currently be provided by the transport media carrying TIPC. When running across UDP, IPSec can be used, when on Ethernet, MACSec is the best option. The TIPC team is currently looking into how to support TLS or DTLS, ether natively or by an addition to OpenSSL. This protocol was originally developed by Jon Paul Maloy at Ericsson during 1996-2005 and was used by that company in cluster applications for several years, before subsequently
Transparent Inter-process Communication
557232
expensive. Processes own resources allocated by the operating system. Resources include memory (for both code and data), file handles, sockets, device handles, windows, and a process control block. Processes are "isolated" by process isolation, and do not share address spaces or file resources except through explicit methods such as inheriting file handles or shared memory segments, or mapping the same file in a shared way – see interprocess communication. Creating or destroying a process is relatively expensive, as resources must be acquired or released. Processes are typically preemptively multitasked, and process switching is relatively expensive, beyond basic cost of context
Thread (computing)
5924462
computing systems, communication between the concurrent components is hidden from the programmer (e.g., by using futures), while in others it must be handled explicitly. Explicit communication can be divided into two classes: Shared memory and message passing concurrency have different performance characteristics. Typically (although not always), the per-process memory overhead and task switching overhead is lower in a message passing system, but the overhead of message passing is greater than for a procedure call. These differences are often overwhelmed by other performance factors. Concurrent computing developed out of earlier work on railroads and telegraphy, from the 19th and early 20th
Concurrent computing
11829256
Exec (Amiga) Exec is the kernel of AmigaOS. It is a 13 KB multitasking microkernel which enabled pre-emptive multitasking in as little as 256 KB of memory (as supplied with the first Amiga 1000s). Exec provided functions for multitasking, memory management, and handling of interrupts and dynamic shared libraries. It acts as a scheduler for tasks running on the system, providing pre-emptive multitasking with prioritized round-robin scheduling. Exec also provides access to other libraries and high-level inter-process communication via message passing. Other comparable microkernels have had performance problems because of the need to copy messages between address spaces. Since the
Exec (Amiga)
126369
2005 a benchmark with 20 million processes was successfully performed with 64-bit Erlang on a machine with 16GB RAM (total 800 bytes/process). Erlang has supported symmetric multiprocessing since release R11B of May 2006. While threads require external library support in most languages, Erlang provides language-level features for creating and managing processes with the aim of simplifying concurrent programming. Though all concurrency is explicit in Erlang, processes communicate using message passing instead of shared variables, which removes the need for explicit locks (a locking scheme is still used internally by the VM). Inter-process communication works via a shared-nothing asynchronous message passing
Erlang (programming language)
83034
terminating the offending process. Depending on the software and kernel design and the specific error in question, the user may receive an access violation error message such as "segmentation fault". In a well designed and correctly implemented multitasking system, a given process can never directly access memory that belongs to another process. An exception to this rule is in the case of shared memory; for example, in the System V inter-process communication mechanism the kernel allocates memory to be mutually shared by multiple processes. Such features are often used by database management software such as PostgreSQL. Inadequate memory protection mechanisms,
Computer multitasking
12981124
through the use of shared kernel memory, rather than the slower IPC system of microkernel designs, which is typically based on message passing. The performance of microkernels was poor in both the 1980s and early 1990s. However, studies that empirically measured the performance of these microkernels did not analyze the reasons of such inefficiency. The explanations of this data were left to "folklore", with the assumption that they were due to the increased frequency of switches from "kernel-mode" to "user-mode", to the increased frequency of inter-process communication and to the increased frequency of context switches. In fact, as guessed in
Kernel (operating system)
3043101
to all the standard Linux inter-process communication mechanisms, shared memory, semaphores, SYSV message queues, pipes and Unix domain sockets. In order to implement cluster wide shared memory – distributed shared memory – OpenSSI uses the CFS "token" system. At any one time a memory segment may be readable by one or more nodes, or writable by one node. If a node without write access to a segment tries to write then the segment is marked unreadable on all other nodes and writable on the current node. If a node without read access tries to read a segment then the current
OpenSSI
1315642
wall, and thus multicore systems have become more widespread, making parallel algorithms of more general use. The cost or complexity of serial algorithms is estimated in terms of the space (memory) and time (processor cycles) that they take. Parallel algorithms need to optimize one more resource, the communication between different processors. There are two ways parallel processors communicate, shared memory or message passing. Shared memory processing needs additional locking for the data, imposes the overhead of additional processor and bus cycles, and also serializes some portion of the algorithm. Message passing processing uses channels and message boxes but this communication
Parallel algorithm
16378345
SIMPL Synchronous Interprocess Messaging Project for LINUX (SIMPL) is a free and open-source project that allows QNX-style synchronous message passing by adding a Linux library using user space techniques like shared memory and Unix pipes to implement codice_1/codice_2/codice_3 inter-process messaging mechanisms. A client thread sending a message is BLOCKED (the process thread execution is temporarily suspended) until the server thread sends a received message acknowledgement, processes the message, and executes a reply. When the server thread replies the client thread becomes READY (unblocked). The server thread typically loops, waiting to receive a message from a client thread. Blocking synchronizes the
SIMPL
2527572
Message queue In computer science, message queues and mailboxes are software-engineering components used for inter-process communication (IPC), or for inter-thread communication within the same process. They use a queue for messaging – the passing of control or of content. Group communication systems provide similar kinds of functionality. The message queue paradigm is a sibling of the publisher/subscriber pattern, and is typically one part of a larger message-oriented middleware system. Most messaging systems support both the publisher/subscriber and message queue models in their API, e.g. Java Message Service (JMS). Message queues provide an asynchronous communications protocol, meaning that the sender and
Message queue
16168181
under automaton's control. I/O automata can be used to model individual components of a distributed system, such as a process, a message channel in a message passing system, or a shared data structure in a shared memory systems. Figure 1 depicts an example of an I/O automaton for a process in an asynchronous message-passing distributed system. In this setting, process P communicates with other processes by using a message passing system. Its output actions are of the form send(m), which represents process P sending a message with contents m to process P. The input actions are of form receive(m), representing
Input/output automaton
1725868
computing today. MPI is not sanctioned by any major standards body; nevertheless, it has become a "de facto" standard for communication among processes that model a parallel program running on a distributed memory system. Actual distributed memory supercomputers such as computer clusters often run such programs. The principal MPI-1 model has no shared memory concept, and MPI-2 has only a limited distributed shared memory concept. Nonetheless, MPI programs are regularly run on shared memory computers, and both MPICH and Open MPI can use shared memory for message transfer if it is available. Designing programs around the MPI model (contrary to
Message Passing Interface
22444
that software developers can program a cluster as if it were a single system, without using message passing (i.e. semaphore-controlled Inter-process Communication). AIX administrators can use this new capability to cluster a pool of AIX nodes. By default, AIX V7.1 pins kernel memory and includes support to allow applications to pin their kernel stack. Pinning kernel memory and the kernel stack for applications with real-time requirements can provide performance improvements by ensuring that the kernel memory and kernel stack for an application is not paged out. AIX 7.2 was announced in October 2015, and released in December 2015. AIX 7.2
IBM AIX
2527576
MQ software on an appliance. Most real-time operating systems (RTOSes), such as VxWorks and QNX, encourage the use of message queueing as the primary inter-process or inter-thread communication mechanism. The resulting tight integration between message passing and CPU scheduling is attributed as a main reason for the usability of RTOSes for real time applications. Early examples of commercial RTOSes that encouraged a message-queue basis to inter-thread communication also include VRTX and pSOS+, both of which date to the early 1980s. The Erlang programming language uses "processes" to provide concurrency; these processes communicate asynchronously using message queuing. In a typical message-queueing
Message queue
1725866
available on advanced machines. In an effort to create a universal standard for message passing, researchers incorporated the most useful features of several systems into MPI, rather than choosing one system to adopt as a standard. They adopted features from systems by IBM, Intel, nCUBE, PVM, Express, P4 and PARMACS. The message-passing paradigm is attractive because of wide portability and can be used in communication for distributed-memory and shared-memory multiprocessors, networks of workstations, and a combination of these elements. The paradigm can apply in multiple settings, independent of network speed or of memory architecture. Support for MPI meetings came in
Message Passing Interface
1344658
for microkernels and nanokernels. Microkernels reduce the number of functionalities provided by the kernel. Those functionalities are then obtained by communicating with servers via IPC, increasing drastically the number of IPC compared to a regular monolithic kernel. Depending on the solution, an IPC mechanism may provide synchronization or leave it up to processes and threads to communicate amongst themselves (e.g. via shared memory). While synchronization will include some information (e.g. whether or not the lock is enabled, a count of processes waiting, etc.) it is not primarily an information-passing communication mechanism "per se". Examples of synchronization primitives are: The following
Inter-process communication
18436708
Shared register In distributed computing, shared-memory systems and message-passing systems are two means of interprocess communication which have been heavily studied. In shared-memory systems, processes communicate by accessing shared data structures. A shared (read-write) register, sometimes just called a register, is a fundamental type of shared data structure which stores a value and has two operations: "Read", which returns the value stored in the register, and "Write", which updates the value stored. Other types of shared data structures include read-modify-write, test-and-set, compare-and-swap etc. The memory location which is concurrently accessed is sometimes called a register. Registers can be classified according
Shared register
6735246
A multi-core processor implements multiprocessing in a single physical package. Designers may couple cores in a multi-core device tightly or loosely. For example, cores may or may not share caches, and they may implement message passing or shared-memory inter-core communication methods. Common network topologies to interconnect cores include bus, ring, two-dimensional mesh, and crossbar. Homogeneous multi-core systems include only identical cores; heterogeneous multi-core systems have cores that are not identical (e.g. big.LITTLE have heterogeneous cores that share the same instruction set, while AMD Accelerated Processing Units have cores that don't even share the same instruction set). Just as with single-processor
Multi-core processor
12963959
caret operator ^) to an ancestor node to repeat behavior, or start a new thread (symbolized by two carets ^^). A behavior tree specifies state changes in components, how data and control is passed between components and how threads interact. There are constructs for creating and breaking relations. There are also constructs for setting and testing states of components as well as mechanisms for inter-process communication that include message passing (events), shared variable blocking and synchronization. For a complete reference to behavior tree notation, version 1.0, see: "Behavior Tree Notation v1.0" (2007) The formal semantics of behavior trees is given
Behavior tree
1725873
e. g. in servers with multiple large shared-memory nodes. The MPI interface is meant to provide essential virtual topology, synchronization, and communication functionality between a set of processes (that have been mapped to nodes/servers/computer instances) in a language-independent way, with language-specific syntax (bindings), plus a few language-specific features. MPI programs always work with processes, but programmers commonly refer to the processes as processors. Typically, for maximum performance, each CPU (or core in a multi-core machine) will be assigned just a single process. This assignment happens at runtime through the agent that starts the MPI program, normally called mpirun or mpiexec.
Message Passing Interface
13048661
with process isolation, limited (controlled) interaction between processes may still be allowed over inter-process communication (IPC) channels such as shared memory, local sockets or Internet sockets. In this scheme, all of the process' memory is isolated from other processes except where the process is allowing input from collaborating processes. System policies may disallow IPC in some circumstances. For example, in mandatory access control systems, subjects with different sensitivity levels may not be allowed to communicate with each other. Notable operating systems that support process isolation: Internet Explorer 4 used process isolation in order to allow separate windowed instances of the
Process isolation
9610544
these resources even after the process migrated. This involves redirection of the I/O data stream over the network and has disadvantages concerning security, performance and reliability. Inter-process communication: messages sent to a process with process ID P on a machine M have to be redirected to the new machine N and the new process ID Q. The machine the process migrated away from needs to keep records of migrated processes. If multiple migration occurs, the overhead increases. Shared memory: if one of a group of cooperating processes migrates away and all these processes use a shared memory segment, then the
Process migration
279228
program. Thread and concurrency support benefited by message passing with IPC mechanisms since tasks now consisted of multiple code threads which Mach could freeze and unfreeze during message handling. This allowed the system to be distributed over multiple processors, either using shared memory directly as in most Mach messages, or by adding code to copy the message to another processor if needed. In a traditional kernel this is difficult to implement; the system has to be sure that different programs don't try to write to the same memory from different processors. However, Mach ports, its process for memory access, make
Mach (kernel)
12981474
are collectively known as the "Unix philosophy". Brian Kernighan and Rob Pike summarize this in "The Unix Programming Environment" as "the idea that the power of a system comes more from the relationships among programs than from the programs themselves". In an era when a standard computer consisted of a hard disk for storage and a data terminal for input and output (I/O), the Unix file model worked quite well, as I/O was generally linear. In the 1980s, non-blocking I/O and the set of inter-process communication mechanisms were augmented with Unix domain sockets, shared memory, message queues, and semaphores, and
Unix
1619335
support and recovery with enhancement to error message text, documentation, and general work at both the kernel and systems program levels. Later Ultrix-32 incorporated some features from 4.3BSD and optionally included DECnet and SNA in addition to the standard TCP/IP, and both the SMTP and DEC's Mail-11 protocols. Notably, Ultrix implemented the inter-process communication (IPC) facilities found in System V (named pipes, messages, semaphores, and shared memory). While the converged Unix from the Sun and AT&T alliance (that spawned the Open Software Foundation or OSF), released late 1986, put BSD features into System V, DEC, as described in Stettner's original
Ultrix
5556310
around a particular programming model is important because it leads to different parallel computers being built with support for the model, thereby facilitating portability of software. In this sense, programming models are referred to as "bridging" between hardware and software. Classifications of parallel programming models can be divided broadly into two areas: process interaction and problem decomposition. Process interaction relates to the mechanisms by which parallel processes are able to communicate with each other. The most common forms of interaction are shared memory and message passing, but interaction can also be implicit (invisible to the programmer). Shared memory is an
Parallel programming model
17975162
processes from SysV style inter-process communication. This prevents processes in different IPC namespaces from using, for example, the SHM family of functions to establish a range of shared memory between the two processes. Instead each process will be able to use the same identifiers for a shared memory region and produce two such distinct regions. UTS namespaces allow a single system to appear to have different host and domain names to different processes. User namespaces are a feature to provide both privilege isolation and user identification segregation across multiple sets of processes. With administrative assistance it is possible to build
Linux namespaces
6047894
they occupy a single place in physical memory, and do not take up space in the page file. If the physical memory occupied by a code section is to be reclaimed, its contents are discarded, and later reloaded directly from the DLL file as necessary. In contrast to code sections, the data sections of a DLL are usually private; that is, each process using the DLL has its own copy of all the DLL's data. Optionally, data sections can be made shared, allowing inter-process communication via this shared memory area. However, because user restrictions do not apply to the use
Dynamic-link library
18532658
Shared memory In computer science, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Shared memory is an efficient means of passing data between programs. Depending on context, programs may run on a single processor or on multiple separate processors. Using memory for communication inside a single program, e.g. among its multiple threads, is also referred to as shared memory. In computer hardware, "shared memory" refers to a (typically large) block of random access memory (RAM) that can be accessed by several different central processing
Shared memory
758548
code in one program from interfering with the operation of another. Even though the memory allocated for specific processes is normally isolated, processes sometimes need to be able to share information. Shared memory is one of the fastest techniques for inter-process communication. Memory is usually classified by access rate into primary storage and secondary storage. Memory management systems, among other operations, also handle the moving of information between these two levels of memory. Memory management Memory management is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate
Memory management
18532665
Library and Qt provides the QSharedMemory class. There is native support for shared memory also in programming languages besides C/C++. For example, PHP provides an API to create shared memory, similar to POSIX functions. Shared memory In computer science, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Shared memory is an efficient means of passing data between programs. Depending on context, programs may run on a single processor or on multiple separate processors. Using memory for communication inside a single program, e.g. among its
Shared memory
2859831
library approach is different than conventional RDBMS systems where the database is essentially a set of distinct processes to which applications connect via some form of inter-process communication. This communication may take the form of a client/server connection spanning over a network or it may be some form of intra-system IPC such as a Unix domain socket connection or a shared memory based connection mechanism. The data for each active TimesTen database is stored in a shared memory segment, allowing multiple TimesTen databases to be active concurrently, and also allowing an application to simultaneously access several TimesTen databases on the
TimesTen
4228685
most services implemented as non-privileged server processes. It provides memory allocation, process management, message passing and synchronisation primitives. The Helios nucleus contains three libraries: the system, server and utility libraries. The utility library provides some basic library routines for C programming that are shared by the other libraries. The system library provides the basic kernel interface, converting C function calls into messages sent to and from the kernel. It implements an abstraction that allows communication between processes regardless of their location in the network. The server library provides name space support functions for writing Helios servers, as described below. The
HeliOS
105065
from one node to another by using the available communication links. Figure (c) shows a parallel system in which each processor has a direct access to a shared memory. The situation is further complicated by the traditional uses of the terms parallel and distributed "algorithm" that do not quite match the above definitions of parallel and distributed "systems" (see below for more detailed discussion). Nevertheless, as a rule of thumb, high-performance parallel computation in a shared-memory multiprocessor uses parallel algorithms while the coordination of a large-scale distributed system uses distributed algorithms. The use of concurrent processes that communicate by message-passing
Distributed computing
18436715
"Read" have the same t-value, order "Write" before "Read". If several "Read"s have the same t-values, order them by the start time. We can use the a SW Snapshot object of size n to construct a MWMR register. The linearization order is as follows. Order "WRITE" operations by t-values. If several "WRITE"s have the same t-value, order the operation with small process ID in front. Insert "READ"s right after "WRITE" whose value they return, breaking ties by process ID and if still tied, break tie by start time. Shared register In distributed computing, shared-memory systems and message-passing systems are two
Shared register
20589
this lack is common amongst many of its contemporary operating systems. The lack of memory protection is because the 68000 CPU does not include a memory management unit and therefore there is no way to enforce protection of memory. Although this speeds and eases inter-process communication because programs can communicate by simply passing a pointer back and forth, the lack of memory protection made the AmigaOS more vulnerable to crashes from badly behaving programs than other multitasking systems that did implement memory protection, and Amiga OS is fundamentally incapable of enforcing any form of security model since any program had
Amiga
4323931
passing simply sends the message to the message bus. The bus stores the message until the receiving process requests messages sent to it. When the receiving process arrives at the result, it sends the result to the message bus, and the message bus holds the message until the original process (or some designated next process) picks up its messages from the message bus. Synchronous communication can be built on top of asynchronous communication by using a Synchronizer. For example, the α-Synchronizer works by ensuring that the sender always waits for an acknowledgement message from the receiver. The sender only sends
Message passing
14320047
processes in different nodes might compete with each other for access to a shared resource. For them, the Lock Service provides entities called lock resources, which in turn, application processes use to coordinate access to those shared resources. The Lock Service provides a simple lock model supporting one locking mode for exclusive access and another one for shared access. The locks provided by the Lock Service are non-recursive. Thus, claiming one lock does not implicitly claim another lock; rather, each lock must be claimed individually. The Message Service specifies APIs for a cluster-wide inter-process communicationsystem. The communication is based on
Application Interface Specification
1725869
explicit shared memory models) has advantages over NUMA architectures since MPI encourages memory locality. Explicit shared memory programming was introduced in MPI-3. Although MPI belongs in layers 5 and higher of the OSI Reference Model, implementations may cover most layers, with sockets and Transmission Control Protocol (TCP) used in the transport layer. Most MPI implementations consist of a specific set of routines directly callable from C, C++, Fortran (i. e., an API) and any language able to interface with such libraries, including C#, Java or Python. The advantages of MPI over older message passing libraries are portability (because MPI has
Message Passing Interface
279229
this well defined and easy to implement, and were made a first-class citizen in that system. The IPC system initially had performance problems, so a few strategies were developed to minimize the impact. Like its predecessor, Accent, Mach used a single shared-memory mechanism for physically passing the message from one program to another. Physically copying the message would be too slow, so Mach relies on the machine's memory management unit (MMU) to quickly map the data from one program to another. Only if the data is written to would it have to be physically copied, a process called "copy-on-write". Messages
Mach (kernel)
6036960
as well as fast client-to-client message passing protocols. LAM/MPI can use TCP/IP, shared memory, Myrinet (GM), or Infiniband (mVAPI) for message passing. LAM features a full implementation of MPI-1 and much of MPI-2. Compliant applications are source code portable between LAM/MPI and any other implementation of MPI. In addition to providing a high-quality implementation of the MPI standard, LAM/MPI offers extensive monitoring capabilities to support debugging. Monitoring happens on two levels. First, LAM/MPI has the hooks to allow a snapshot of process and message status to be taken at any time during an application run. This snapshot includes all aspects
LAM/MPI
7148119
as not having any shared access to mutable memory. The bird/nest mechanism resembles the communication in the Actor model, but with the additional power to be able to pass nests around and for a process to hold more than one nest (which is also true in Janus). A difference between communication in the Actor model and in ToonTalk is that ToonTalk preserves the order of the messages; however, ToonTalk can also provide an indeterministic merge of message streams. ToonTalk ToonTalk is a computer programming system intended to be programmed by children. The "Toon" part stands for cartoon. The system's presentation
ToonTalk
4953029
a translator can convey the message. When writing, the choice of words represent the relationship between the reader and the writer so more thought, and care should be invested in the text since it may be thoroughly analysed by the recipient. Intercultural communication principles Inter-cultural communication principles guide the process of exchanging meaningful and unambiguous information across cultural boundaries, in a way that preserves mutual respect and minimises antagonism. For these purposes, culture is a shared system of symbols, beliefs, attitudes, values, expectations, and norms of behaviour. It refers to coherent groups of people whether resident wholly or partly within
Intercultural communication principles
14260543
a cooperative thread enters the state of waiting for asynchronous input, another thread of the program may run. The feature of TNSDL is the actor model. Processes are meant to be designed as event-driven finite state machines. Inter-process communication is done by asynchronous message passing. The OUTPUT command sends a message, while INPUT statements define the expected messages. Timers, from TNSDL perspective, are delayed messages. Just like ordinary messages, timer expiration is handled by the INPUT statement. The SET command starts and the RESET command cancels a timer. State machines can be optionally used, for example, to prevent accepting certain
TNSDL
1725872
programs still work under MPI implementations compliant with the MPI-2 standard. "MPI-3" includes new Fortran 2008 bindings, while it removes deprecated C++ bindings as well as many deprecated routines and MPI objects. MPI is often compared with Parallel Virtual Machine (PVM), which is a popular distributed environment and message passing system developed in 1989, and which was one of the systems that motivated the need for standard parallel message passing. Threaded shared memory programming models (such as Pthreads and OpenMP) and message passing programming (MPI/PVM) can be considered as complementary programming approaches, and can occasionally be seen together in applications,
Message Passing Interface
11627534
license. Global Arrays Global Arrays, or GA, is the library developed by scientists at Pacific Northwest National Laboratory for parallel computing. GA provides a friendly API for shared-memory programming on distributed-memory computers for multidimensional arrays. The GA library is a predecessor to the GAS (global address space) languages currently being developed for high-performance computing. The GA toolkit has additional libraries including a Memory Allocator (MA), Aggregate Remote Memory Copy Interface (ARMCI), and functionality for out-of-core storage of arrays (ChemIO). Although GA was initially developed to run with TCGMSG, a message passing library that came before the MPI standard (Message Passing
Global Arrays
11627532
Global Arrays Global Arrays, or GA, is the library developed by scientists at Pacific Northwest National Laboratory for parallel computing. GA provides a friendly API for shared-memory programming on distributed-memory computers for multidimensional arrays. The GA library is a predecessor to the GAS (global address space) languages currently being developed for high-performance computing. The GA toolkit has additional libraries including a Memory Allocator (MA), Aggregate Remote Memory Copy Interface (ARMCI), and functionality for out-of-core storage of arrays (ChemIO). Although GA was initially developed to run with TCGMSG, a message passing library that came before the MPI standard (Message Passing Interface),
Global Arrays
3676987
to supply information to one or more people. A communication process is defined as information that is shared with the intent that the receiver understands the message that the business intended to send. The communication process was once thought of as having the source of the message, which is then encoded, put through the chosen communication channel, which is then decoded by the recipient and then received. Throughout the middle of the channel there is the potential for noise to distort the message being sent. Once the receiver has the message they then give feedback to the original source, where
Marketing communications
9889910
computers built with transputer microprocessors by INMOS, or similar architectures. Occam was an early process-oriented language developed for the Transputer. Some derivations have evolved from the message passing paradigm of Occam to enable uniform efficiency when porting applications between distributed memory and shared memory parallel computers . The first such derived example appears in the programming language Ease designed at Yale University in 1990. Similar models have appeared since in the loose combination of SQL databases and objected oriented languages such as Java, often referred to as object-relational models and widely used in large scale distributed systems today. The paradigm
Process-oriented programming
7848972
optional. Other resources are mostly memory and various in-kernel objects such as Inter-process communication shared memory segments and network buffers. Each resource can be seen from /proc/user_beancounters and has five values associated with it: current usage, maximum usage (for the lifetime of a container), barrier, limit, and fail counter. The meaning of barrier and limit is parameter-dependent; in short, those can be thought of as a soft limit and a hard limit. If any resource hits the limit, the fail counter for it is increased. This allows the owner to detect problems by monitoring /proc/user_beancounters in the container. A live
OpenVZ
868690
provides high-speed communication capability that fully exploits the features of IXS and shared memory. It can be used for both intra- and inter-node parallelization. An MPI process is assigned to an AP in the flat parallelization, or to a PN that contains microtasks or OpenMP threads in the hybrid parallelization. MPI libraries are designed and optimizedcarefully to achieve highest performance of communication on the ES architecture in both of the parallelization manner. High Performance Fortrans (HPF) Principal users of ES are considered to be natural scientists who are not necessarily familiar with the parallel programming or rather dislike it. Accordingly,
Earth Simulator
5556311
efficient means of passing data between processes. In a shared-memory model, parallel processes share a global address space that they read and write to asynchronously. Asynchronous concurrent access can lead to race conditions, and mechanisms such as locks, semaphores and monitors can be used to avoid these. Conventional multi-core processors directly support shared memory, which many parallel programming languages and libraries, such as Cilk, OpenMP and Threading Building Blocks, are designed to exploit. In a message-passing model, parallel processes exchange data through passing messages to one another. These communications can be asynchronous, where a message can be sent before the
Parallel programming model
2230854
Server Message Block In computer networking, Server Message Block (SMB), one version of which was also known as Common Internet File System (CIFS, ), operates as an application-layer network protocol mainly used for providing shared access to files, printers, and serial ports and miscellaneous communications between nodes on a network. It also provides an authenticated inter-process communication mechanism. Most usage of SMB involves computers running Microsoft Windows, where it was known as "Microsoft Windows Network" before the introduction of Active Directory. Corresponding Windows services are LAN Manager Server (for the server component) and LAN Manager Workstation (for the client component).
Server Message Block
12964833
robots and various robotic sensors. Orca describes its goals as: They also state: "To be successful, we think that a framework with such objectives must be: general, flexible and extensible; sufficiently robust, high-performance and full-featured for use in commercial applications, yet sufficiently simple for experimentation in university research environments." They describe their approach as: Orca software is released under LGPL and GPL licenses. OpenRDK is an open-source software framework for robotics for developing loosely coupled modules. It provides transparent concurrency management, inter-process (via sockets) and intra-process (via shared memory) blackboard-based communication and a linking technique that allows for input/output data
Robotics middleware
9824849
MXU was actually a Lenkurt 914E Subscriber Loop Carrier. When integrated with the GTD-5 EAX, it used a custom software load that permitted message communication with the remainder of the system. Most communication within the GTD-5 was performed via direct memory-mapped I/O. The APC and each TPC were each connected to three common memory units. These common memory units each contained 16 megabytes of memory which were allocated to shared data structures, both dynamic structures related to dynamic call data and static (protected) data related to the office database. The APC, TPC, and TCUs all connected to a smaller shared
GTD-5 EAX
1289515
and 1980s. However, vector processors—both as CPUs and as full computer systems—have generally disappeared. Modern processor instruction sets do include some vector processing instructions, such as with Freescale Semiconductor's AltiVec and Intel's Streaming SIMD Extensions (SSE). Concurrent programming languages, libraries, APIs, and parallel programming models (such as algorithmic skeletons) have been created for programming parallel computers. These can generally be divided into classes based on the assumptions they make about the underlying memory architecture—shared memory, distributed memory, or shared distributed memory. Shared memory programming languages communicate by manipulating shared memory variables. Distributed memory uses message passing. POSIX Threads and OpenMP
Parallel computing
1725877
include collective communication and dynamic in-process management. Communicators can be partitioned using several MPI commands. These commands include codice_1, where each process joins one of several colored sub-communicators by declaring itself to have that color. A number of important MPI functions involve communication between two specific processes. A popular example is codice_2, which allows one specified process to send a message to a second specified process. Point-to-point operations, as these are called, are particularly useful in patterned or irregular communication, for example, a data-parallel architecture in which each processor routinely swaps regions of data with specific other processors between calculation
Message Passing Interface
105073
lot of interaction between the two fields. For example, the Cole–Vishkin algorithm for graph coloring was originally presented as a parallel algorithm, but the same technique can also be used directly as a distributed algorithm. Moreover, a parallel algorithm can be implemented either in a parallel system (using shared memory) or in a distributed system (using message passing). The traditional boundary between parallel and distributed algorithms (choose a suitable network vs. run in any given network) does not lie in the same place as the boundary between parallel and distributed systems (shared memory vs. message passing). In parallel algorithms, yet
Distributed computing
3042582
Temporary file Temporary files, or foo files (.TMP), are files created to temporarily contain information while a new file is being made. It may be created by computer programs for a variety of purposes; principally when a program cannot allocate enough memory for its tasks, when the program is working on data bigger than the architecture's address space, or as a primitive form of inter-process communication. Modern operating systems employ virtual memory, however programs that use large amounts of data (e.g. video editing) may need to create temporary file(s). Most operating systems offer primitives such as pipes, sockets or shared
Temporary file
2230869
to clients using SMB 2.x and higher. SMB works through a client-server approach, where a client makes specific requests and the server responds accordingly. One section of the SMB protocol specifically deals with access to filesystems, such that clients may make requests to a file server; but some other sections of the SMB protocol specialize in inter-process communication (IPC). The Inter-Process Communication (IPC) share, or ipc$, is a network share on computers running Microsoft Windows. This virtual share is used to facilitate communication between processes and computers over SMB, often to exchange data between computers that have been authenticated. Developers
Server Message Block
11717827
LINX (IPC) LINX is a new generation of the OSE link handler for inter-process communications (IPC) that provides high performance and robust functionality developed by ENEA AB in Sweden. LINX was released as free and open-source software, subject to the requirements of the GNU General Public License (GPL), version 2. LINX was ported later on Linux, works with same success on both OSE and Linux kernels. Is possible to interconnect a Linux machine with an OSE one and have a direct communication path between processes that run under different kernels. Utilizing direct message passing, LINX scales from DSPs and microcontrollers
LINX (IPC)
5880138
performs a data dependence analysis of the loop to determine whether each iteration of the loop can be executed independently of the others. Data dependence can sometimes be dealt with, but it may incur additional overhead in the form of message passing, synchronization of shared memory, or some other method of processor communication. The second pass attempts to justify the parallelization effort by comparing the theoretical execution time of the code after parallelization to the code's sequential execution time. Somewhat counterintuitively, code does not always benefit from parallel execution. The extra overhead that can be associated with using multiple processors
Automatic parallelization
3928476
program are implemented by identical computation on all nodes rather than computing the result on one node and sending it to the others. Nowadays, the programmer is isolated from the details of the message passing by standard interfaces, such as PVM and MPI. Distributed memory is the programming style used on parallel supercomputers from homegrown Beowulf clusters to the largest clusters on the Teragrid. On a shared memory machine (a computer with several CPUs that access the same memory space), messages can be sent by depositing their contents in a shared memory area. This is often the most efficient way
SPMD
9253977
the source file on the disk once the last process is finished. These memory-mapped files are suitable for working with extremely large source files. Non-persisted files are not associated with a file on a disk. When the last process has finished working with the file, the data is lost. These files are suitable for creating shared memory for inter-process communications (IPC). The major reason to choose memory mapped file I/O is performance. Nevertheless, there can be tradeoffs. The standard I/O approach is costly due to system call overhead and memory copying. The memory-mapped approach has its cost in minor page
Memory-mapped file
3043136
to communicate using inter-process communications mechanisms as if they were running on the same machine. On some SSI systems this can even include shared memory (can be emulated with Software Distributed shared memory). In most cases inter-node IPC will be slower than IPC on the same machine, possibly drastically slower for shared memory. Some SSI clusters include special hardware to reduce this slowdown. Some SSI systems provide a "cluster address", a single address visible from outside the cluster that can be used to contact the cluster as if it were one machine. This can be used for load balancing inbound
Single system image
6064750
Windows NT's undocumented Native API, and as such is not available to applications for direct use. However, it can be used indirectly in the following instances: (A)LPC is implemented using kernel "port" objects, which are securable (with ACLs, allowing e.g. only specific SIDs to use them) and allow identification of the process on the other side of the connection. Individual messages are also securable: applications can set per-message SIDs, and also test for changes of the security context in the token associated with the (A)LPC message. The typical communication scenario between the server and the client is as follows: (A)LPC
Local Inter-Process Communication
2726571
commonly called a "thread", and "team" for what is now commonly called a "process" consisting of multiple threads sharing an address space. Communication between threads in V uses synchronous message passing, with short, fixed-length messages that can include access rights for the receiver to read or write part of the sender's address space before replying. The same message-passing interface is used both between threads within one process, between threads of different processes within one machine, and between threads on different machines connected by a local Ethernet. A thread receiving a message is not required to reply to it before receiving
V (operating system)
14733806
by the blob leading string. Available message transports include TCP, PGM (reliable multicast), inter-process communication (IPC) and inter-thread communication (ITC). The ZeroMQ core library performs very well due to its internal threading model, and can outperform conventional TCP applications in terms of throughput by utilizing an automatic message batching technique. ZeroMQ implements ZMTP, the ZeroMQ Message Transfer Protocol. ZMTP defines rules for backward interoperability, extensible security mechanisms, command and message framing, connection metadata, and other transport-level functionality. A growing number of projects implement ZMTP directly as an alternative to using the full ZeroMQ implementations. iMatix CEO Pieter Hintjens registered the
ZeroMQ
2528111
by the provider. The call invokes provider services to route and deliver the message. Once it has sent the message, the client can continue to do other work, confident that the provider retains the message until a receiving client retrieves it. The message-based model, coupled with the mediation of the provider, makes it possible to create a system of loosely coupled components. MOM comprises a category of inter-application communication software that generally relies on asynchronous message-passing, as opposed to a request-response architecture. In asynchronous systems, message queues provide temporary storage when the destination program is busy or not connected. In
Message-oriented middleware
4022042
the Tuxedo interfaces as the basis of their standards such as X/Open XA and XATMI. The Tuxedo developers published papers about it in the early 1990s. Later it became the basis of some research projects. Tuxedo is at its core a message routing and queuing system. Requests are sent to named services and Tuxedo uses memory based inter-process communication facilities to queue the requests to servers. The requester is unaware of where the server that actually processes the request is located or how it is implemented. In essence, Tuxedo provided the elements of service-oriented architecture (SOA) decades before the phrase
Tuxedo (software)
18532662
generally held in memory once and mapped to multiple processes, and only pages that had to be customized for the individual process (because a symbol resolved differently there) are duplicated, usually with a mechanism known as copy-on-write that transparently copies the page when a write is attempted, and then lets the write succeed on the private copy. POSIX provides a standardized API for using shared memory, "POSIX Shared Memory". This uses the function codice_1 from sys/mman.h. POSIX interprocess communication (part of the POSIX:XSI Extension) includes the shared-memory functions codice_2, codice_3, codice_4 and codice_5. Unix System V provides an API for
Shared memory
3675976
volatile variable assignment and read has a corresponding memory access. Without the codice_1 keyword, the compiler knows a variable does not need to be reread from memory at each use, because there should not be any writes to its memory location from any other thread or process. According to the C++11 ISO Standard, the volatile keyword is only meant for use for hardware access; do not use it for inter-thread communication. For inter-thread communication, the standard library provides codice_24 templates. The Java programming language also has the codice_1 keyword, but it is used for a somewhat different purpose. When applied
Volatile (computer programming)
1630616
but soon named Guardian for its ability to protect all data from machine faults or software faults. In contrast to all other commercial operating systems, Guardian was based on message passing as the basic way for all processes to interact, without shared memory, regardless of where the processes were running. This approach easily scaled to multiple-computer clusters and helped isolate corrupted data before it propagated. All file system processes and all transactional application processes were structured as master/slave pairs of processes running in separate cpus. The slave process periodically took snapshots of the master's memory state, and took over the
Tandem Computers
14733890
expressed by algorithms and data structures. Protocols are to communication what algorithms or programming languages are to computations. Operating systems usually contain a set of cooperating processes that manipulate shared data to communicate with each other. This communication is governed by well-understood protocols, which can be embedded in the process code itself. In contrast, because there is no shared memory, communicating systems have to communicate with each other using a shared transmission medium. Transmission is not necessarily reliable, and individual systems may use different hardware or operating systems. To implement a networking protocol, the protocol software modules are interfaced with
Communication protocol
3003342
mmap(2) is sometimes used for Interprocess Communication (IPC). On modern operating systems mmap(2) is typically preferred to the System V IPC Shared Memory facility. The main difference between System V shared memory (shmem) and memory mapped I/O (mmap) is that SystemV shared memory is persistent: unless explicitly removed by a process, it is kept in memory and remains available until the system is shut down. mmap'd memory is not persistent between application executions (unless it is backed by a file). /* Does not work on OS X, as you can't mmap over /dev/zero */ int main(void) sample output: Mmap In
Mmap
10779762
Tilera Tilera Corporation was a fabless semiconductor company focusing on manycore embedded processor design. The company shipped multiple processors, including the TILE64, TILE"Pro"64, and the TILE"Pro"36, TILE-Gx72, TILE-Gx36, TILE-Gx16 and TILE-Gx9. After a series of company acquisitions. Tilera's intellectual property was eventually acquired by Mellanox, which now ships products that descend from the original Tilera designs. In 1990, Anant Agarwal led a team of researchers at Massachusetts Institute of Technology to develop scalable multi-processor system built out of large numbers of single chip processors. Alewife machines integrated both shared memory and user-level message passing for inter-node communications. In 1997, Agarwal
Tilera
4323937
meaningless to the remote program (however, a relative address might in fact be usable if the receiver had an "exact" copy of, at least some of, the sender's memory in advance). Web browsers and web servers are examples of processes that communicate by message passing. A URL is an example of a way of referencing resources that does not depend on exposing the internals of a process. A subroutine call or method invocation will not exit until the invoked computation has terminated. Asynchronous message passing, by contrast, can result in a response arriving a significant time after the request message
Message passing
13160617
IUCV IUCV (Inter User Communication Vehicle) is a data transfer mechanism in IBM VM line of operating systems. IUCV allows establishing point to point communication channels, either between 2 virtual machines or between a virtual machine and hypervisor services. In effect, IUCV provides a form of message-based interaction between virtual machines that anticipated the client/server interaction between network connected physical machines that emerged later on distributed systems. IUCV is implemented by CP (the VM hypervisor) and controls all aspects of session establishments, message passing and flow control. Before a virtual machine can use the IUCV service, it must first indicate
IUCV
61271
a question, or they might sign a sarcastic-large slow yes to convey a different nonverbal meaning. The sign yes is the verbal message while the other movements add nonverbal meaning to the message. Over time the forms of and ideas about communication have evolved through the continuing progression of technology. Advances include communications psychology and media psychology, an emerging field of study. The progression of written communication can be divided into three "information communication revolutions": Communication is thus a process by which meaning is assigned and conveyed in an attempt to create shared understanding. Gregory Bateson called it "the replication
Communication
6064749
Local Inter-Process Communication The Local Inter-Process Communication (LPC, often also referred to as Local Procedure Call or Lightweight Procedure Call) is an internal, undocumented inter-process communication facility provided by the Microsoft Windows NT kernel for lightweight IPC between processes on the same computer. As of Windows Vista, LPC has been rewritten as Asynchronous Local Inter-Process Communication (ALPC, often also Advanced Local Procedure Call) in order to provide a high-speed scalable communication mechanism required to efficiently implement User-Mode Driver Framework (UMDF), whose user-mode parts require an efficient communication channel with UMDF's components in the executive. The (A)LPC interface is part of
Local Inter-Process Communication
13262389
"Agent" (or an "Actor"), which is an isolated entity that executes in parallel with other Agents. In Axum parlance, this is referred to as the agents executing in separate "isolation domains"; objects instantiated within a domain cannot be directly accessed from another. Agents are loosely coupled (i.e., the number of dependencies between agents is minimal) and do not share resources like memory (unlike the shared memory model of C# and similar languages); instead a message passing model is used. To co-ordinate agents or having an agent request the resources of another, an explicit message must be sent to the agent.
Axum (programming language)
7821969
Marking an area of memory with "Data Cache Block: Zero" (allocating a line but setting its contents to zero instead of loading from main memory) and discarding it after use ('Data Cache Block: Invalidate', signaling that main memory didn't receive any updated data) the cache is made to behave as a scratchpad. Generality is maintained in that these are hints and the underlying hardware will function correctly regardless of actual cache size. Regarding interprocessor communication in a multicore setup, there are similarities between the Cell's inter-localstore DMA and a shared L2 cache setup as in the Intel Core 2 Duo
Scratchpad memory
12747897
to achieve the required system operation. Messages are used for Control functions. Channels can be established between a pair of Devices (inter-Device communication), or between one Device and many Devices (broadcast communication), or in the case of the Message Channel, from all devices to all other devices (shared). Control Space is divided into three types of channels: Framing, Guide, and Message. The Framing Channel occupies Slots 0 and 96 of each Frame. (Since all Subframe lengths divide 96, these Slots are always available for the purpose.) Slot 0 holds a fixed Frame Sync symbol (1011), while Slot 96 holds 4
SLIMbus
2347970
OpenMP uses a portable, scalable model that gives programmers a simple and flexible interface for developing parallel applications for platforms ranging from the standard desktop computer to the supercomputer. An application built with the hybrid model of parallel programming can run on a computer cluster using both OpenMP and Message Passing Interface (MPI), such that OpenMP is used for parallelism "within" a (multi-core) node while MPI is used for parallelism "between" nodes. There have also been efforts to run OpenMP on software distributed shared memory systems, to translate OpenMP into MPI and to extend OpenMP for non-shared memory systems. OpenMP
OpenMP