Wikipedia: Discrete Fourier Transform
Performs a discrete Fourier transform on axis k of arr. The length of k must be an integer power of two. (See power-of-two?.) The scaling convention is determined by the parameter dft-convention, which defaults to the convention used in signal processing.
The transform is done in parallel using max-math-threads threads.
The inverse of array-axis-fft, performed by parameterizing the forward transform on (dft-inverse-convention).
Performs a discrete Fourier transform on each axis of arr using array-axis-fft.