FFTW_threading

A simple program to verify that the built-in threading in FFTW3 is working.

How to compile: gcc -lfftw3_omp -lfftw3 -lm -fopenmp threading_test.c -o threading_test.o

How to run: export OMP_NUM_THREADS=NUMTHREADS

where NUMTHREADS is 8 or the number of threads you wish to utilize.

Timings with 1000 162x162x162 FFTs:

FFTW_ESTIMATE threads time (s) speedup 1 252 1.0 2 124 2.0 4 67 3.8 8 35 7.2 16 20 12.6 32 11 22.9

FFTW_MEASURE threads time (s) speedup 1 195 1.0 2 117 1.7 4 57 3.4 8 32 6.1 16 17 11.5 32 10 19.5

FFTW_PATIENT threads time (s) speedup 1 198 1 2 96 2 4 48 4 8 26 8 16 15 13 32 8 25