Efficient Algorithms for Array Redistribution

Dynamic redistribution of arrays is required very often in programs on distributed memory parallel computers. This paper presents eecient algorithms for redistribution between diierent cyclic(k) distributions, as deened in High Performance Fortran. We rst propose special optimized algorithms for a cyclic(x) to cyclic(y) redistribution when x is a multiple of y, or y is a multiple of x. We then propose two algorithms, called the GCD method and the LCM method, for the general cyclic(x) to cyclic(y) redistribution when there is no particular relation between x and y. We have implemented these algorithms on the Intel Touchstone Delta, and nd that they perform well for diierent array sizes and number of processors.