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Distributed Shared Memory
In computer science, distributed shared memory (DSM) is a form of memory architecture where physically separated memories can be addressed as a single shared address space. The term "shared" does not mean that there is a single centralized memory, but that the address space is shared—i.e., the same physical address on two Processor (computing), processors refers to the same location in memory. Distributed global address space (DGAS), is a similar term for a wide class of software and hardware implementations, in which each node (networking), node of a computer cluster, cluster has access to shared memory architecture, shared memory in addition to each node's private (i.e., not shared) Random-access memory, memory. Overview DSM can be achieved via software as well as hardware. Hardware examples include cache coherence circuits and network interface controllers. There are three ways of implementing DSM: * Page (computer memory), Page-based approach using virtual memory * Sha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, applied disciplines (including the design and implementation of Computer architecture, hardware and Software engineering, software). Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence Protocol
In computer architecture, cache coherence is the uniformity of shared resource data that is stored in multiple local caches. In a cache coherent system, if multiple clients have a cached copy of the same region of a shared memory resource, all copies are the same. Without cache coherence, a change made to the region by one client may not be seen by others, and errors can result when the data used by different clients is mismatched. A cache coherence protocol is used to maintain cache coherency. The two main types are snooping and directory-based protocols. Cache coherence is of particular relevance in multiprocessing systems, where each CPU may have its own local cache of a shared memory resource. Overview In a shared memory multiprocessor system with a separate cache memory for each processor, it is possible to have many copies of shared data: one copy in the main memory and one in the local cache of each processor that requested it. When one of the copies of data is ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MOSIX
MOSIX is a proprietary distributed operating system. Although early versions were based on older UNIX systems, since 1999 it focuses on Linux clusters and grids. In a MOSIX cluster/grid there is no need to modify or to link applications with any library, to copy files or login to remote nodes, or even to assign processes to different nodes – it is all done automatically, like in an SMP. History MOSIX has been researched and developesince 1977at The Hebrew University of Jerusalem by the research team of Prof. Amnon Barak. So far, ten major versions have been developed. The first version, called MOS, for ''Multicomputer OS'', (1981–83) was based on Bell Lab's Seventh Edition Unix and ran on a cluster of PDP-11 computers. Later versions were based on Unix System V Release 2 (1987–89) and ran on a cluster of VAX and NS32332-based computers, followed by a BSD/OS-derived version (1991–93) for a cluster of 486/Pentium computers. Since 1999 MOSIX is tuned to Linux for x86 pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OpenSSI
OpenSSI is an open-source single-system image clustering system. It allows a collection of computers to be treated as one large system, allowing applications running on any one machine access to the resources of all the machines in the cluster. OpenSSI is based on the Linux operating system and was released as an open source project by Compaq in 2001. It is the final stage of a long process of development, stretching back to LOCUS, developed in the early 1980s. Description OpenSSI allows a cluster of individual computers (''nodes'') to be treated as one large system. Processes run on any node have full access to the resources of all nodes. Processes can be migrated from node to node automatically to balance system utilization. Inbound network connections can be directed to the least loaded node available. OpenSSI is designed to be used for both high performance and high availability clusters. It is possible to create an OpenSSI cluster with no single point of failure, f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kerrighed
Kerrighed is an open source single-system image (SSI) cluster software project. The project started in October 1998 at the Paris research group The French National Institute for Research in Computer Science and Control. From 2006 to 2011, the project was mainly developed by Kerlabs. In January, 2012 the Linux clustering mission of Kerlabs was adopted by a new company: We Cluster, Inc. headquartered in Pacific Grove, California. January 18, 2012: Kerrighed 3.0 has been ported to Ubuntu 12.04 with Linux Kernel v3.2. Background Kerrighed is implemented as an extension to the Linux operating system. It helps scientific applications such as numerical simulations to use more power. Such applications may be using OpenMP, Message Passing Interface, and/or a Posix multithreaded programming model. Kerrighed implements a set of global resource management services that aim at making resource distribution transparent to the applications, at managing resource sharing in and between applicat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Message Passing Interface
The Message Passing Interface (MPI) is a portable message-passing standard designed to function on parallel computing architectures. The MPI standard defines the syntax and semantics of library routines that are useful to a wide range of users writing portable message-passing programs in C, C++, and Fortran. There are several open-source MPI implementations, which fostered the development of a parallel software industry, and encouraged development of portable and scalable large-scale parallel applications. History The message passing interface effort began in the summer of 1991 when a small group of researchers started discussions at a mountain retreat in Austria. Out of that discussion came a Workshop on Standards for Message Passing in a Distributed Memory Environment, held on April 29–30, 1992 in Williamsburg, Virginia. Attendees at Williamsburg discussed the basic features essential to a standard message-passing interface and established a working group to continu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Section
In concurrent programming, concurrent accesses to shared resources can lead to unexpected or erroneous behavior. Thus, the parts of the program where the shared resource is accessed need to be protected in ways that avoid the concurrent access. One way to do so is known as a critical section or critical region. This protected section cannot be entered by more than one process or thread at a time; others are suspended until the first leaves the critical section. Typically, the critical section accesses a shared resource, such as a data structure, peripheral device, or network connection, that would not operate correctly in the context of multiple concurrent accesses. Need for critical sections Different code or processes may consist of the same variable or other resources that must be read or written but whose results depend on the order in which the actions occur. For example, if a variable is to be read by process A, and process B must write to the variable at the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sequential Invocations And Responses In DSM
In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is called the ''length'' of the sequence. Unlike a set, the same elements can appear multiple times at different positions in a sequence, and unlike a set, the order does matter. Formally, a sequence can be defined as a function from natural numbers (the positions of elements in the sequence) to the elements at each position. The notion of a sequence can be generalized to an indexed family, defined as a function from an ''arbitrary'' index set. For example, (M, A, R, Y) is a sequence of letters with the letter "M" first and "Y" last. This sequence differs from (A, R, M, Y). Also, the sequence (1, 1, 2, 3, 5, 8), which contains the number 1 at two different positions, is a valid sequence. Sequences can be ''finite'', as in these examples, or ''infini ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intel QuickPath Interconnect
The Intel QuickPath Interconnect (QPI) is a scalable processor interconnect developed by Intel which replaced the front-side bus (FSB) in Xeon, Itanium, and certain desktop platforms starting in 2008. It increased the scalability and available bandwidth. Prior to the name's announcement, Intel referred to it as Common System Interface (CSI). Earlier incarnations were known as Yet Another Protocol (YAP) and YAP+. QPI 1.1 is a significantly revamped version introduced with Sandy Bridge-EP ( Romley platform). QPI was replaced by Intel Ultra Path Interconnect (UPI) in Skylake-SP Xeon processors based on LGA 3647 socket. Background Although sometimes called a "bus", QPI is a scalable interconnect fabric with dynamic routing capabilities. It was designed to compete with HyperTransport that had been used by Advanced Micro Devices (AMD) since around 2003. Intel developed QPI at its Massachusetts Microprocessor Design Center (MMDC) by members of what had been the Alpha Development G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dsm States
DSM or dsm may refer to: Science and technology * Deep space maneuver * Deep sea mining * Design structure matrix or dependency structure matrix, a representation of a system or project * Diagnostic and Statistical Manual of Mental Disorders ** DSM-5, the fifth edition of the DSM ** DSM-5-TR, text revision of the DSM-5 * Digital Standard MUMPS, a version of the MUMPS programming language created by Digital Equipment Corporation * Digital surface model, another term for digital elevation model, used to digitally map topography * DiskStation Manager, a Linux-based operating system used by Synology * Distributed shared memory, software and hardware implementations in which each cluster node accesses a large shared memory * Door status monitor, a device that reads whether a door is open or closed * Dynamic scattering mode, a principle used by the first operational liquid-crystal display * Dynamic spectrum management, a technique to increase bandwidth over DSL * Doctor of Medicine, awar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Coherence
Memory coherence is an issue that affects the design of computer systems in which two or more Central processing unit, processors or Multi core, cores share a common area of memory (computers), memory. In a uniprocessor system (where there exists only one core), there is only one processing element doing all the work and therefore only one processing element that can read or write from/to a given memory location. As a result, when a value is changed, all subsequent read operations of the corresponding memory location will see the updated value, even if it is cache (computing), cached. Conversely, in multiprocessor (or Multi core, multicore) systems, there are two or more processing elements working at the same time, and so it is possible that they simultaneously access the same memory location. Provided none of them changes the data in this location, they can share it indefinitely and cache it as they please. But as soon as one updates the location, the others might work on an out-o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
