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Segmented Scan
In computer science, a segmented scan is a modification of the prefix sum with an equal-sized array of flag bits to denote segment boundaries on which the scan should be performed.Blelloch, Guy E. "Scans as primitive parallel operations." Computers, IEEE Transactions on 38.11 (1989): 1526-1538. Example In the following, the '1' flag bits indicate the beginning of each segment. : \begin 1 & 2 & 3 & 4 & 5& 6 &\text\\ \hline 1 & 0 & 0 & 1 & 0 & 1 &\text\\ \hline 1 & 3 & 6 & 4& 9 & 6 &\text\\ \end ;Group1 * 1 = 1 * 3 = 1 + 2 * 6 = 1 + 2 + 3 ;Group2 * 4 = 4 * 9 = 4 + 5 ;Group3 * 6 = 6 An alternative method used by High Performance Fortran is to begin a new segment at every transition of flag value. An advantage of this representation is that it is useful with both prefix and suffix (backwards) scans without changing its interpretation. In HPF, Fortran logical data type is used to represent segments. So the equivalent flag array for the above example would be as follows: \begin 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (including the design and implementation of hardware and software). Computer science is generally considered an area of academic research and distinct from computer programming. Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and for preventing security vulnerabilities. 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 repositories ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prefix Sum
In computer science, the prefix sum, cumulative sum, inclusive scan, or simply scan of a sequence of numbers is a second sequence of numbers , the sums of prefixes (running totals) of the input sequence: : : : :... For instance, the prefix sums of the natural numbers are the triangular numbers: : Prefix sums are trivial to compute in sequential models of computation, by using the formula to compute each output value in sequence order. However, despite their ease of computation, prefix sums are a useful primitive in certain algorithms such as counting sort,. and they form the basis of the scan higher-order function in functional programming languages. Prefix sums have also been much studied in parallel algorithms, both as a test problem to be solved and as a useful primitive to be used as a subroutine in other parallel algorithms.. Abstractly, a prefix sum requires only a binary associative operator ⊕, making it useful for many applications from calculating well-separated pair ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Performance Fortran
High Performance Fortran (HPF) is an extension of Fortran 90 with constructs that support parallel computing, published by the ''High Performance Fortran Forum'' (HPFF). The HPFF was convened and chaired by Ken Kennedy of Rice University. The first version of the HPF Report was published in 1993. Building on the array syntax introduced in Fortran 90, HPF uses a data parallel model of computation to support spreading the work of a single array computation over multiple processors. This allows efficient implementation on both SIMD and MIMD style architectures. HPF features included: * New Fortran statements, such as FORALL, and the ability to create PURE (side effect free) procedures * Compiler directives for recommended distributions of array data * ''Extrinsic procedure'' interface for interfacing to non-HPF parallel procedures such as those using message passing * Additional library routines - including environmental inquiry, parallel prefix/suffix (e.g., 'scan'), data sca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flattening Transformation
The flattening transformation is an algorithm that transforms nested data parallelism into flat data parallelism. It was pioneered by Guy Blelloch as part of the NESL programming language. The flattening transformation is also sometimes called vectorization, but is completely unrelated to automatic vectorization. The original flattening algorithm was concerned solely with first-order multidimensional arrays containing primitive types, but was extended to handle higher-order and recursive data types in the work on Data Parallel Haskell. Overview Flattening works by ''lifting'' functions to operate on arrays instead of on single values. For example, a function f : A \rightarrow B is lifted to a function f' : \rightarrow /math>. This means an expression map~f~x can be replaced with an application of the lifted function: f'~x. Intuitively, flattening thus works by replacing all function applications with applications of the corresponding lifted function. After flattening, ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concurrent Algorithms
Concurrent means happening at the same time. Concurrency, concurrent, or concurrence may refer to: Law * Concurrence, in jurisprudence, the need to prove both ''actus reus'' and ''mens rea'' * Concurring opinion (also called a "concurrence"), a legal opinion which supports the conclusion, though not always the reasoning, of the majority. * Concurrent estate, a concept in property law * Concurrent resolution, a legislative measure passed by both chambers of the United States Congress * Concurrent sentences, in criminal law, periods of imprisonment that are served simultaneously Computing * Concurrency (computer science), the property of program, algorithm, or problem decomposition into order-independent or partially-ordered units * Concurrent computing, the overlapping execution of multiple interacting computational tasks * Concurrence (quantum computing), a measure used in quantum information theory * Concurrent Computer Corporation, an American computer systems manufacturer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
