FFT factory with option to use fftwf wisdom file
This applies to Linux only. On Windows the KISS FFT is implemented in place of FFTW thus no difference is expected.
With the FFT factory the FFTW plan structures are preserved during the lifetime of the application. Allocating these plans take time. Depending on the FFT size even on powerful machines this can take several seconds so they are valuable resources not to be wasted. This factory system allows the re-cycling of plans and saves time where a plan of the same size has already been allocated and is not used anymore.
In addition to this the possibility to use a so called "wisdom file". The wisdom file is built offline using the fftwf-wisdom command on the same machine where SDRangel is run. This command runs the lengthy process of testing the hardware to choose the right code to perform FFTs and saves the result to the file thus speeding up the allocation of plans. A process that takes several seconds will take only milliseconds to execute when using this file.
A typical fftwf-wisdom command that can produce an efficient wisdom file in the context of SDRangel is: fftwf-wisdom -v -n -o ~/fftw-wisdom f128 f256 f512 f1024 f2048 f4096 f8192 b128 b256 b512 b1024 b2048 b4096 b8192 To use this file when invoking SDRangel you use its -w command line option: sdrangel -w ~/fftw-wisdom