Found 700 Articles for Computer Science

Parallel algorithms are those specially devised for parallel computers. The idealized parallel algorithms are those written for the PRAM models if no physical constraints or communication overheads are imposed. In the real world, an algorithm is considered efficient only if it can be cost-effectively implemented on physical machines. In this sense, all machine-implementable algorithms must be architecture-dependent. This means the effects of communication overhead and architectural constraints cannot be ignored.Characteristics of Parallel AlgorithmThere are various characteristics of parallel algorithm which are as follows −Deterministic versus nondeterministic − It is only deterministic algorithms are implementable on real machines. Our study is ... Read More

A distributed-memory multicomputer system is modeled in the figure. The system includes multiple computers known as nodes, related by a message-passing network. Each node is an independent computer including a processor, local memory, and sometimes connected disks or I/O peripherals.The message-passing network supports point-to-point static connections among the nodes. All local memories are private and are applicable only by local processors. For this method, traditional multicomputer has been referred to as no-remote-memory-access (NORMA) machines.This condition will constantly be deleted in future multicomputer with distributed shared memories. Internode communication is carried out by passing messages through the static connection network.Multicomputer Generations ... Read More

VLIW stands for Very-Long Instruction Word (VLIW) architectures. It is an appropriate alternative for exploiting instruction-level parallelism (ILP) in programs, especially, for performing more than one basic (primitive) instruction at a time.These processors include various functional units, fetch from the instruction cache a Very-Long Instruction Word including various primitive instructions, and dispatch the whole VLIW for parallel implementation.These capacities are exploited by compilers that produce code that has grouped separate primitive instructions executable in parallel. The processors have associatively simple control logic because they do not implement any dynamic scheduling nor reordering of operations.The main goal of VLIW is to ... Read More

Data routing networks are used for inter PE data exchange. Data routing networks can be static or dynamic. In a multicomputer network, data routing is achieved by messages among multiple computer nodes.Routing network reduces the time required for data exchange and thus system performance is enhanced. Commonly used data routing functions are shifting, rotation, permutations, broadcast, multicast, personalized communication, shuffle, etc.There are various data routing functions which are as follows −Permutations − Let there are n objects, and then there are n permutations by which n objects can be recorded. The set of all permutations form a permutation group concerning ... Read More

The topology of an interconnection network can be static or dynamic. Static networks are created point-to-point direct connections which will not alter during implementation. Dynamic networks are applied with switched channels, which are dynamically constructed to connect the communication demand in user programs.Static Networks − Static networks are used for fixed connections amid subsystems of a centralized system or various computing nodes of a distributed system. Dynamic networks include buses, crossbar switches, multistage networks, which are provide used in shared-memory multiprocessors. Both types of networks have also been applying for inter PE data routing in SIMD computers.In general, a network ... Read More

There are few experimental data flow computer projects. The associates at MIT have developed a tagged token architecture for constructing data flow computers.The global architecture incorporates n processing elements (PEs) inter-connected by an n x n routing network. The complete system provides pipelined data flow operations in all n PEs. Inter PE communications are completed by the pipelined routing network.In each PE, the machine offers a low-level token matching structure that sends off only those instructions whose input data are already accessible. Each datum is identified with the address of the instruction to which it belongs and the context in ... Read More

Traditional computers are founded on a control flow structure by which the series of program implementation is particularly established in the user program. Data flow computers have a high degree of parallelism at the fine-grain instruction-level reduction computers are based on a demand-driven method which commences operation based on the demand for its result by other computations.Data flow & control flow computers − There are mainly two sorts of computers as data flow computers are connectional computers depends on the Von Neumann machine. It transfers out instructions under program flow control whereas the control flow computer implements instructions under the ... Read More

The most popular parallel computers are those that implement programs in MIMD mode. There are two major types of parallel computers such as shared memory multiprocessor & message-passing multi computers. The main difference between multiprocessors & multicomputer lies in memory sharing and the structure used for interprocessor communication.The processor in the multiprocessor system communicates with each other through a shared variable in common memory. Each computer node in a multicomputer system has local memory, unshared with different nodes. Inter-process communication is done through message passing among nodes.Three shared memory multiprocessor models are as follows −UMA ModelUMA stands for Uniform memory ... Read More

There are different level of parallelism which are as follows −Instruction Level − At instruction level, a grain is consist of less than 20 instruction called fine grain. Fine-grain parallelism at this level may range from two thousand depending on an individual program single instruction stream parallelism is greater than two but the average parallelism at instruction level is around fine rarely exceeding seven in an ordinary program.For scientific applications, the average parallel is in the range of 500 to 300 Fortran statements executing concurrently in an idealized environment.Loop Level − It embraces iterative loop operations. A loop may contain ... Read More

There are various conditions of Parallelism which are as follows −Data and resource dependencies − A program is made up of several parts, so the ability to implement various program segments in parallel is needed that each segment should be autonomous regarding the other segment. Dependencies in various segments of a program may be in various forms like resource dependency, control depending & data depending.A dependence graph can define the relation. The program statements are defined by nodes and the directed edge with multiple labels displays the ordered relation among the statements. After analyzing the dependence graph, it can be ... Read More