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In the C programming language, Duff's device is a way of manually implementing loop unrolling by interleaving two syntactic constructs of C: the do-while loop and a switch statement. Its discovery is credited to Tom Duff in November 1983, when Duff was working for Lucasfilm and used it to speed up a real-time animation program.
A loop-switch sequence [1] (also known as the for-case paradigm [2] or Anti-Duff's Device) is a programming antipattern where a clear set of steps is implemented as a switch-within-a-loop. The loop-switch sequence is a specific derivative of spaghetti code. It is not necessarily an antipattern to use a switch statement within a loop—it is ...
Switch statements function somewhat similarly to the if statement used in programming languages like C/C++, C#, Visual Basic .NET, Java and exist in most high-level imperative programming languages such as Pascal, Ada, C/C++, C#, [1]: 374–375 Visual Basic .NET, Java, [2]: 157–167 and in many other types of language, using such keywords as ...
A loop is a sequence of statements which is specified once but which may be carried out several times in succession. The code "inside" the loop (the body of the loop, shown below as xxx) is obeyed a specified number of times, or once for each of a collection of items, or until some condition is met, or indefinitely. When one of those items is ...
Exit a protected region of code. Base instruction 0xDE leave.s <int8 (target)> Exit a protected region of code, short form. Base instruction 0xFE 0x0F localloc: Allocate space from the local memory pool. Base instruction 0xC6 mkrefany <class> Push a typed reference to ptr of type class onto the stack. Object model instruction 0x5A mul: Multiply ...
In computer science, software pipelining is a technique used to optimize loops, in a manner that parallels hardware pipelining.Software pipelining is a type of out-of-order execution, except that the reordering is done by a compiler (or in the case of hand written assembly code, by the programmer) instead of the processor.
Loops using while, repeat until or do, and for statements; switch a.k.a. case statements, a form of multiway branching; These new language mechanisms replaced equivalent flows which previously would have been written using gotos and ifs. Multi-way branching replaces the "computed goto" in which the instruction to jump to is determined ...
Loop interchange on this example can improve the cache performance of accessing b(j,i), but it will ruin the reuse of a(i) and c(i) in the inner loop, as it introduces two extra loads (for a(i) and for c(i)) and one extra store (for a(i)) during each iteration. As a result, the overall performance may be degraded after loop interchange.