Stuff

Comparison of Gwyddion 2.7 simpleFFT transform speed with FFTW3.1 in using ESTIMATE plans (FFTs are typically one-shot in Gwyddion) and FFT hum (the old Gwyddion FFT procedure).

The test was performed on Athlon64 with -O2 optimization, with split real and imaginary arrays (as is normal in Gwyddion) of stride 1. Repeated FFTW3 means a plan was created and then executed many times (how many exactly depended on the transform size, larger ones were executed fewer times to keep the testing time finite), one-shot FFTW3 means a plan was created, executed and destroyed for each transform. FFT hum has no planning and simpleFFT has a very simple fixed planning method, executed each time.

Normalized execution time is the execution time divided by n log(n), where n is the transform size. This nicely visualizes overheads and failures to scale.