Efficient methods for kr→r and r→kr array redistribution

Array redistribution is usually required to enhance algorithm performance in many parallel programs on distributed memory multicomputers. Since it is performed at run-time, there is performance tradeoff between the efficiency of new data decomposition for a subsequent phase of an algorithm and the cost of redistributing data among processors. We present efficient algorithms for array redistribution. The most significant improvement of our algorithms is that a processor does not need to construct the send/receive data sets for a redistribution. Based on the packing/unpacking information that derived from the BLOCK-CYCLIC(kr) to BLOCK-CYCLIC(r) redistribution (or vice versa), a processor can pack/unpack array elements into (from) messages directly. To evaluate the performance of our methods, we have implemented our methods along with Thakur´s (1994) methods on an IBM SP2 parallel machine. The results show that the execution time of our algorithms is approximately 5% to 27% faster than that of Thakur´s methods