Hierarchical Communication Optimization for FFT
Mohit Kumar, Preeti Malakar · 2022
Fast Fourier Transforms (FFT) are used to solve various scientific and engineering problems. For example, computational fluid dynamics (CFD) simulations employ a pseudospectral method to solve flow simulations using Fast Fourier transforms (FFT). FFT requires global communications among all parallel processes; this often increases communication times. We present FFTOpt, a communication optimization library that leverages hierarchical communications within a compute node and across nodes of a large-scale system. This is a generic library that may optimize any code or application that uses MPI Alltoall and MPI Sendrecv without any dependency on the system or application. FFTOpt also uses topology information and runtime details about node allocation to aggregate at node and switch levels to reduce communication times. We tested FFTOpt in our department cluster (uses MPICH MPI library and connected by Ethernet) and PARAM Sanganak supercomputer (uses Intel MPI library and connected by Infiniband) of IIT Kanpur using the FFTW, FFTK and P3DFFT libraries. FFTOpt reduces communication time by up to 63%.