Multiprocessor out-of-core FFTs with distributed memory and parallel disks (extended abstract)

This paper extends an earlier out-of-core Fast Fourier Transform (FFT) method for a uniprocessor with the Parallel Disk Model (PDM) to use multiple processors. Four out-of-core multiprocessor methods are examined. Operationally, these methods di er in the size of \minibutter y" computed in memory and how the data are organized on the disks and in the distributed memory of the multiprocessor. The methods also perform di ering amounts of I/O and communication. Two of them have the remarkable property that even though they are computing the FFT on a multiprocessor, all interprocessor communication occurs outside the mini-butter y computations. Performance results on a small workstation cluster indicate that except for unusual combinations of problem size and memory size, the methods that do not perform interprocessor communication during the mini-butter y computations require approximately 86% of the time of those that do. Moreover, the faster methods are much easier to implement.