Glancing at your code diff, I think you're missing the bit-reversed permutation....

nayuki on June 29, 2020 | parent | context | favorite | on: Implementing the Exponential Function

Glancing at your code diff, I think you're missing the bit-reversed permutation. Either way, feel free to steal from: https://www.nayuki.io/page/free-small-fft-in-multiple-langua...