guile-ffi-fftw/README.md

guile-ffi-fftw

This is a minimal set of Guile FFI bindings for FFTW's ‘guru interface’, www.fftw.org/fftw3_doc/Guru-Interface.html#Guru-Interface

It provides two functions:

• fftw-dft! transform-rank sign in out
• fftw-dft transform-rank sign in

The array arguments in and out can be of type c32 (complex float) or c64 (complex double), and of any rank not smaller than transform-rank. The transform axes are last; please check the online help.

The bindings show how to interface between Guile and array libraries taking dense arrays as arguments. FFTW makes it easy by supporting arbitrary ranks and strides —which should be the norm!

The FFTW libraries are loaded with dynamic-link, either through the environment variable GUILE_FFI_FFTW_LIBFFTW3_PATH, or on the default path. If only the float or only the double versions of the library are found, then fftw-dft! and fftw-dft will only support either c32 or c64 arguments.

These bindings being minimal, there is no support for computing & reusing plans, or split r/i transforms, or anything but straight complex DFTs. Contributions are welcome!

Running the tests

The tests use SRFI-64.

$GUILE -L mod -s test/test-ffi-fftw.scm

To do

• Arbitrary transform axes (make transform-rank into a list transform-axes).

Links

• https://www.fftw.org/
• https://savannah.gnu.org/projects/guile-fftw - set of bindings using a C extension