Experimental analysis of multi-mode fast Fourier transforms on the PASM parallel processing system

A detailed study is presented of parallel fast Fourier transform programs executing on the prototype of the PASM parallel processing system. Detailed execution time measurements using specialized timing hardware were made for complete fast Fourier transforms (FFTs) and for SIMD, MIMD, and hybrid SIMD/MIMD implementations. The component measurements isolated the effects of floating-point operations, interconnection network transfer operations, and program control overhead. Using these detailed measurements, an expression for projecting the execution time for an M-point FFT executing on M/2 PASM processing elements is derived. This expression is then used to obtain an accurate extrapolation of the execution time and speedup of the MIMD, SIMD, and hybrid programs to a full 1024-processor PASM system. Overall, the experimental results demonstrate the value of the multimode capability of PASM and the stability of PASM for computationally intensive algorithms such as the FFT