34 investigate alternate fft implementations - Githubissues

OpenPIV / openpiv-c--qt

C++ with Qt frontend (superfast) version of OpenPIV

http://www.openpiv.net

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34 investigate alternate fft implementations #36

Closed timdewhirst closed 1 year ago

timdewhirst commented 1 year ago

Add pocket_fft:

Test methodology:

run process -i exp1_001_a.tiff exp1_001_b.tiff -o 0.0625 -f <correlation type> for real, complex, pocket, pocket_real
run 10 times
find average

The test produces 40560 32x32 interrogation areas and is the total time i.e. loading images, analysing, writing data to output.

Correlation types:

complex:
- two real to complex image conversions
- two complex forward FFTs
- multiplication by complex conjugate
- single reverse complex FFT
real:
- combine two real images into single complex image
- single complex forward FFT
- unravel into two complex images
- multiplication by complex conjugate
- single reverse complex FFT
pocket: as complex except using pocket_fft for FFT
pocket_real: as real except using pocket_fft for FFT

Test run on Intel i5-2520M dual core with hyper threading/ubuntu 22.04.1 LTS:	correlation	average time (s)	improvement
complex	3.254	0.0%
real	2.958	9.1%
pocket	2.375	27.1%
pocket_real	2.305	29.1%

Test run on MacBook Pro M1 PRO, OS X 13.0.1	correlation	average time (s)	improvement
complex	0.537	0.0%
real	0.455	15.2%
pocket	0.305	43.2%
pocket_real	0.281	47.7%

Fastest time on M1 PRO is ~7us per interrogation area.