From 994c8e29bac4a5969cffb9eb913d2e74692bc71c Mon Sep 17 00:00:00 2001 From: skal Date: Tue, 24 Mar 2026 07:52:25 +0100 Subject: fix(fft): replace iterative twiddle with direct cosf/sinf, add tests A-E fft_radix2 now computes wr=cosf(angle*k)/wi=sinf(angle*k) directly per k, eliminating float drift over long iteration runs. Iterative approach documented in comment for reference. Tests A-E added (bit-reverse, small-N DFT, twiddle drift, DCT small/large N). arrays_match tolerance reverted to 5e-3. TODO.md updated. handoff(Gemini): fft twiddle fix complete, 38/38 tests passing. --- src/audio/fft.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'src/audio/fft.h') diff --git a/src/audio/fft.h b/src/audio/fft.h index df37ad5..6a54742 100644 --- a/src/audio/fft.h +++ b/src/audio/fft.h @@ -8,6 +8,9 @@ #include +// Bit-reversal permutation (in-place). Exposed for testing. +void bit_reverse_permute(float* real, float* imag, size_t N); + // Forward FFT: Time domain → Frequency domain // Input: real[] (length N), imag[] (length N, can be zeros) // Output: real[] and imag[] contain complex frequency bins -- cgit v1.2.3