Locks in FFTW is limiting CPU efficiency when multi-threading

11/21/19 Haiwang Yu 1

Noise filtering with sticky code mitigation (SCM)https://github.com/WireCell/wire-cell-toolkit/pull/8

NF SP

http://www.fftw.org/fftw3_doc/Thread-safety.html

Protodune::StickyCodeMitig::apply()

FFT in SCM

Reading Eigen FFT code

11/21/19 Haiwang Yu 2

https://eigen.tuxfamily.org/dox/unsupported/ei__fftw__impl_8h_source.html

Plan caching

Thread unsafe

Eigen FFTW implementation has this plan caching feature!

Waveform::dft ⟹ Waveform::FFT::dft

11/21/19 Haiwang Yu 3

Plan cache destroyed in ‘Eigen::FFT’ dtor

Could create an ‘FFT’ instance for each INode using FFT. Then Plan cache could live the whole running period.Not many chances to hit the planner call locks

In the SCM code, FFT was performed 4 times per channel!A lot of creating new plans.

Plan caching FFT in MT mode

11/21/19 Haiwang Yu 4

SCM with Pgrapher - ST

11/21/19 Haiwang Yu 5

Next: mbCoherentNoiseSub

11/21/19 Haiwang Yu 6

updated with plan caching FFT:pdStickyCodeMitigpdOneChannelNoisepdRelGainCalib – no fft used

next:mbCoherentNoiseSub

SCM with Pgrapher - ST

11/21/19 Haiwang Yu 7

no fft

w/ fft no plan caching

w/ fft plan caching