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In addition, the loop control variables and number of operations inside the unrolled loop structure have to be chosen carefully so that the result is indeed the same as in the original code (assuming this is a later optimization on already working code). For example, consider the implications if the iteration count were not divisible by 5.
In computer science, a for-loop or for loop is a control flow statement for specifying iteration. Specifically, a for-loop functions by running a section of code repeatedly until a certain condition has been satisfied. For-loops have two parts: a header and a body. The header defines the iteration and the body is the code executed once per ...
The basic idea of loop unrolling is that the number of instructions executed in a loop can be reduced by reducing the number of loop tests, sometimes reducing the amount of time spent in the loop. For example, in the case of a loop with only a single instruction in the block code, the loop test will typically be performed for every iteration of ...
The types of objects that can be iterated across (my_list in the example) are based on classes that inherit from the library class ITERABLE. The iteration form of the Eiffel loop can also be used as a boolean expression when the keyword loop is replaced by either all (effecting universal quantification) or some (effecting existential ...
Sometimes within the body of a loop there is a desire to skip the remainder of the loop body and continue with the next iteration of the loop. Some languages provide a statement such as continue (most languages), skip , [ 8 ] cycle (Fortran), or next (Perl and Ruby), which will do this.
In loop-carried dependence, statements in an iteration of a loop depend on statements in another iteration of the loop. Loop-Carried Dependence uses a modified version of the dependence notation seen earlier. Example of loop-carried dependence where S1[i] ->T S1[i + 1], where i indicates the current iteration, and i + 1 indicates the next ...
The original loop iteration space is n by n. The accessed chunk of array a[i, j] is also n by n. When n is too large and the cache size of the machine is too small, the accessed array elements in one loop iteration (for example, i = 1, j = 1 to n) may cross cache lines, causing cache misses.
For example, if all reaching definitions for the operands of some simple expression are outside of the loop, the expression can be moved out of the loop. Recent work by Moyen, Rubiano and Seiller uses data-flow dependence analysis [ 1 ] to detect not only invariant commands but larger code fragments such as an inner loop.