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Normalized Loop
In computer science, a normalized loop (sometimes called well-behaved loop), is a loop in which the loop variable starts at 0 (or any constant) and gets incremented by one at every iteration until the exit condition is met. Normalized loops are very important for compiler theory, loop dependence analysis as they simplify the data dependence analysis. Well-behaved loops A well behaved loop is normally of the form: for ( i = 0; i < MAX; i++ ) a = b + 5; Because the increment is unitary and constant, it's very easy to see that, if both ''a'' and ''b'' are bigger than MAX, this loop will never access memory outside the allocated range. Non-normalized loops A non-normalized loop may begin at different indexes, increment by not-unitary amounts and have exit conditions complicated to define. Such loops are hard to op ...[...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] |
Compiler Theory
In computing, a compiler is a computer program that Translator (computing), translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that translate source code from a high-level programming language to a lower level language, low-level programming language (e.g. assembly language, object code, or machine code) to create an executable program.Compilers: Principles, Techniques, and Tools by Alfred V. Aho, Ravi Sethi, Jeffrey D. Ullman - Second Edition, 2007 There are many different types of compilers which produce output in different useful forms. A ''cross-compiler'' produces code for a different Central processing unit, CPU or operating system than the one on which the cross-compiler itself runs. A ''bootstrap compiler'' is often a temporary compiler, used for compiling a more permanent or better optimised compiler for a language. Related software ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Dependence Analysis
In computer science, loop dependence analysis is a process which can be used to find dependencies within iterations of a loop with the goal of determining different relationships between statements. These dependent relationships are tied to the order in which different statements access memory locations. Using the analysis of these relationships, execution of the loop can be organized to allow multiple processors to work on different portions of the loop in parallel. This is known as parallel processing. In general, loops can consume a lot of processing time when executed as serial code. Through parallel processing, it is possible to reduce the total execution time of a program through sharing the processing load among multiple processors. The process of organizing statements to allow multiple processors to work on different portions of a loop is often referred to as parallelization. In order to see how we can exploit parallelization, we have to first analyze the dependencies wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Dependence
Data ( , ) are a collection of discrete or continuous values that convey information, describing the quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted formally. A datum is an individual value in a collection of data. Data are usually organized into structures such as tables that provide additional context and meaning, and may themselves be used as data in larger structures. Data may be used as variables in a computational process. Data may represent abstract ideas or concrete measurements. Data are commonly used in scientific research, economics, and virtually every other form of human organizational activity. Examples of data sets include price indices (such as the consumer price index), unemployment rates, literacy rates, and census data. In this context, data represent the raw facts and figures from which useful information can be extracted. Data are collected using techniques such as m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dependence Analysis
In compiler theory, dependence analysis produces execution-order constraints between statements/instructions. Broadly speaking, a statement ''S2'' depends on ''S1'' if ''S1'' must be executed before ''S2''. Broadly, there are two classes of dependencies--control dependencies and data dependencies. Dependence analysis determines whether it is safe to reorder or parallelize statements. Control dependencies Control dependency is a situation in which a program instruction executes if the previous instruction evaluates in a way that allows its execution. A statement ''S2'' is ''control dependent'' on ''S1'' (written S1\ \delta^c\ S2) if and only if ''S2s execution is conditionally guarded by ''S1''. ''S2'' is ''control dependent'' on ''S1'' if and only if S1 \in PDF(S2) where PDF(S) is the post dominance frontier of statement S. The following is an example of such a control dependence: S1 if x > 2 goto L1 S2 y := 3 S3 L1: z := y + 1 Here, ''S2'' only runs if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Transformation
In compiler theory, loop optimization is the process of increasing execution speed and reducing the overheads associated with loops. It plays an important role in improving cache performance and making effective use of parallel processing capabilities. Most execution time of a scientific program is spent on loops; as such, many compiler optimization techniques have been developed to make them faster. Representation of computation and transformations Since instructions inside loops can be executed repeatedly, it is frequently not possible to give a bound on the number of instruction executions that will be impacted by a loop optimization. This presents challenges when reasoning about the correctness and benefits of a loop optimization, specifically the representations of the computation being optimized and the optimization(s) being performed.In the book Reasoning About Program Transformations', Jean-Francois Collard discusses in depth the general question of representing exec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Splitting
Loop splitting is a compiler optimization An optimizing compiler is a compiler designed to generate code that is optimized in aspects such as minimizing program execution time, memory usage, storage size, and power consumption. Optimization is generally implemented as a sequence of op ... technique. It attempts to simplify a loop or eliminate dependencies by breaking it into multiple loops which have the same bodies but iterate over different contiguous portions of the index range. Loop peeling Loop peeling is a special case of loop splitting which splits any problematic first (or last) few iterations from the loop and performs them outside of the loop body. Suppose a loop was written like this: int p = 10; for (int i=0; i<10; ++i) Notice that p = 10 only for the first iteration, and for all other iterations, p = i - 1. A compiler can take advantage of this by [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Fusion
Loop fission (or loop distribution) is a compiler optimization in which a loop is broken into multiple loops over the same index range with each taking only a part of the original loop's body. The goal is to break down a large loop body into smaller ones to achieve better utilization of locality of reference. This optimization is most efficient in multi-core processors that can split a task into multiple tasks for each processor. Conversely, loop fusion (or loop jamming) is a compiler optimization and loop transformation which replaces multiple loops with a single one. Loop fusion does not always improve run-time speed. On some architectures, two loops may actually perform better than one loop because, for example, there is increased data locality within each loop. One of the main benefits of loop fusion is that it allows temporary allocations to be avoided, which can lead to huge performance gains in numerical computing languages such as Julia when doing elementwise operations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Interchange
Loop or LOOP may refer to: Brands and enterprises * Loop (mobile), a Bulgarian virtual network operator and co-founder of Loop Live * Loop, clothing, a company founded by Carlos Vasquez in the 1990s and worn by Digable Planets * Loop Mobile, an Indian mobile phone operator * Loop Internet, an internet service provider in Pennsylvania, United States * Loop, a reusable container program announced in 2019 by TerraCycle Geography * Loop, Germany, a municipality in Schleswig-Holstein * Loop (Texarkana), a roadway loop around Texarkana, Arkansas, United States * Loop, Blair County, Pennsylvania, United States * Loop, Indiana County, Pennsylvania, United States * Loop, West Virginia, United States * Loop 101, a semi-beltway of the Phoenix Metropolitan Area * Loop 202, a semi-beltway of the Phoenix Metropolitan Area * Loop 303, a semi-beltway of the Phoenix Metropolitan Area * Chicago Loop, the downtown neighborhood of Chicago bounded by the elevated railway The Loop ** L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Skewing
The polyhedral model (also called the polytope method) is a mathematical framework for programs that perform large numbers of operations -- too large to be explicitly enumerated -- thereby requiring a ''compact'' representation. Nested loop programs are the typical, but not the only example, and the most common use of the model is for loop nest optimization in program optimization. The polyhedral method treats each loop iteration within nested loops as lattice points inside mathematical objects called polytope, polyhedra, performs affine transformations or more general non-affine transformations such as Loop tiling, tiling on the polytopes, and then converts the transformed polytopes into equivalent, but optimized (depending on targeted optimization goal), loop nests through polyhedra scanning. Simple example Consider the following example written in C (programming language), C: const int n = 100; int i, j; int a[n][n] = ; for (i = 1; i < n; i++) for (i = 0; i < n; i++) [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Automatic Parallelization
Automatic parallelization, also auto parallelization, or autoparallelization refers to converting sequential code into multi-threaded and/or vectorized code in order to use multiple processors simultaneously in a shared-memory multiprocessor ( SMP) machine. Fully automatic parallelization of sequential programs is a challenge because it requires complex program analysis and the best approach may depend upon parameter values that are not known at compilation time. The programming control structures on which autoparallelization places the most focus are loops, because, in general, most of the execution time of a program takes place inside some form of loop. There are two main approaches to parallelization of loops: pipelined multi-threading and cyclic multi-threading. For example, consider a loop that on each iteration applies a hundred operations, and runs for a thousand iterations. This can be thought of as a grid of 100 columns by 1000 rows, a total of 100,000 operations. Cyc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Automatic Vectorization
Automatic vectorization, in parallel computing, is a special case of automatic parallelization, where a computer program is converted from a scalar implementation, which processes a single pair of operands at a time, to a vector implementation, which processes one operation on multiple pairs of operands at once. For example, modern conventional computers, including specialized supercomputers, typically have vector operations that simultaneously perform operations such as the following four additions (via SIMD or SPMD hardware): :\begin c_1 & = a_1 + b_1 \\ c_2 & = a_2 + b_2 \\ c_3 & = a_3 + b_3 \\ c_4 & = a_4 + b_4 \end However, in most programming languages one typically writes loops that sequentially perform additions of many numbers. Here is an example of such a loop, written in C: for (i = 0; i < n; i++) c = a + b [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
