chowdsp_fft

chowdsp_fft is a fork of the pffft library for computing Fast Fourier Transforms. This fork adds a couple of optimizations, most importantly the ability to use AVX intrinsics for single-precision FFTs on compatible platforms.

Disclaimer

This library has only been tested for power-of-2 FFT sizes. My understanding is that pffft supports some additional FFT sizes. I imagine many of those sizes will work with this implementation as well, but please test first and report back!

Using chowdsp_fft with AVX SIMD Intrinsics

The provided CMake configuration will compile chowdsp_fft as static library containing both the SSE and AVX implementations (so long as the compiler supports compiling with AVX). From there, when the user creates an FFT "setup" object, an option is provided to use the AVX implementation if it's available on the host system. When this option is enabled, several things happen:

• When compiling for a platform that doesn't support AVX (e.g. an ARM CPU), the option is ignored.
• When running on a compatible platform, the library will first check if the host CPU supports AVX intrinsics. If not, the library will fall back to the SSE implementation.
• Next the library will check if the requested FFT size is large enough for the AVX implementation to work. Smaller FFT sizes will also fall back to the SSE implementation.

Using with JUCE

If you're using this library as part of a CMake project that uses JUCE, the CMake configuration for this library will also generate a JUCE module that you can link to chowdsp::chowdsp_fft_juce, which allows the FFT implementations to be used by juce::dsp::FFT.

In order to avoid symbols clashing, you must make sure that the juce_dsp module is not being compiled alongside chowdsp_fft_juce. If you are in control of all the modules being used, this should be pretty easy to do, but if you're using third-party modules that require juce_dsp then I'm not sure what you should do. Since this module will compile the juce_dsp code for you, you may want to manually define JUCE_MODULE_AVAILABLE_juce_dsp=1 so that other modules in your system are aware.

License

Copyright (c) 2024 Jatin Chowdhury ( jatin@chowdsp.com )
Copyright (c) 2013  Julien Pommier ( pommier@modartt.com )

Based on original fortran 77 code from FFTPACKv4 from NETLIB,
authored by Dr Paul Swarztrauber of NCAR, in 1985.

As confirmed by the NCAR fftpack software curators, the following
FFTPACKv5 license applies to FFTPACKv4 sources. My changes are
released under the same terms.

FFTPACK license:
http://www.cisl.ucar.edu/css/software/fftpack5/ftpk.html

Copyright (c) 2004 the University Corporation for Atmospheric
Research ("UCAR"). All rights reserved. Developed by NCAR's
Computational and Information Systems Laboratory, UCAR,
www.cisl.ucar.edu.

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  Laboratory, the University Corporation for Atmospheric Research,
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- Redistributions of source code must retain the above copyright
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