FFTW is fastest when it has small prime factors according to its manual. If there is the option to pad the input data, then with radix 2 FFT algorithms this is done with a “next power of 2” type function. However if the length is just over a power of 2, at large sizes this can lead to arrays of al…

Optimal Power of N for FFTW

rafael.guerra August 3, 2022, 4:06pm 8

Linking related thread.

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