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c-kzg-4844
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Do some namespacing for the FFT routines

This commit is contained in:
Ben Edgington 2021-02-02 12:42:38 +00:00
parent 3ee603fbdc
commit 4ee33f7aba
3 changed files with 19 additions and 19 deletions
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20
src/fft_fr.c
View File

@ -17,7 +17,7 @@
#include "fft_fr.h"
// Slow Fourier Transform (simple, good for small sizes)
void slow_ft(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l) {
void fft_fr_slow(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l) {
blst_fr v, last, tmp;
for (uint64_t i = 0; i < l; i++) {
blst_fr jv = in[offset];
@ -36,10 +36,10 @@ void slow_ft(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_f
}
// Fast Fourier Transform
void fast_ft(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l) {
void fft_fr_fast(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l) {
uint64_t half = l / 2;
fft_helper(out, in, offset, stride * 2, roots, roots_stride * 2, l / 2);
fft_helper(out + half, in, offset + stride, stride * 2, roots, roots_stride * 2, l / 2);
fft_fr_helper(out, in, offset, stride * 2, roots, roots_stride * 2, l / 2);
fft_fr_helper(out + half, in, offset + stride, stride * 2, roots, roots_stride * 2, l / 2);
for (uint64_t i = 0; i < half; i++) {
blst_fr y_times_root;
blst_fr x = out[i];
@ -49,17 +49,17 @@ void fast_ft(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_f
}
}
void fft_helper(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l) {
void fft_fr_helper(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l) {
// TODO: Tunable parameter
if (l <= 4) {
slow_ft(out, in, offset, stride, roots, roots_stride, l);
fft_fr_slow(out, in, offset, stride, roots, roots_stride, l);
} else {
fast_ft(out, in, offset, stride, roots, roots_stride, l);
fft_fr_fast(out, in, offset, stride, roots, roots_stride, l);
}
}
// The main entry point for forward and reverse FFTs
void fft (blst_fr *out, blst_fr *in, FFTSettings *fs, bool inv, uint64_t n) {
void fft_fr (blst_fr *out, blst_fr *in, FFTSettings *fs, bool inv, uint64_t n) {
uint64_t stride = fs->max_width / n;
assert(n <= fs->max_width);
assert(is_power_of_two(n));
@ -67,11 +67,11 @@ void fft (blst_fr *out, blst_fr *in, FFTSettings *fs, bool inv, uint64_t n) {
blst_fr inv_len;
fr_from_uint64(&inv_len, n);
blst_fr_eucl_inverse(&inv_len, &inv_len);
fft_helper(out, in, 0, 1, fs->reverse_roots_of_unity, stride, fs->max_width);
fft_fr_helper(out, in, 0, 1, fs->reverse_roots_of_unity, stride, fs->max_width);
for (uint64_t i = 0; i < fs->max_width; i++) {
blst_fr_mul(&out[i], &out[i], &inv_len);
}
} else {
fft_helper(out, in, 0, 1, fs->expanded_roots_of_unity, stride, fs->max_width);
fft_fr_helper(out, in, 0, 1, fs->expanded_roots_of_unity, stride, fs->max_width);
}
}

8
src/fft_fr.h
View File

@ -17,7 +17,7 @@
#include "c-kzg.h"
#include "fft_util.h"
void slow_ft(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l);
void fast_ft(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l);
void fft_helper(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l);
void fft (blst_fr *out, blst_fr *in, FFTSettings *fs, bool inv, uint64_t n);
void fft_fr_slow(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l);
void fft_fr_fast(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l);
void fft_fr_helper(blst_fr *out, blst_fr *in, uint64_t offset, uint64_t stride, blst_fr *roots, uint64_t roots_stride, uint64_t l);
void fft_fr (blst_fr *out, blst_fr *in, FFTSettings *fs, bool inv, uint64_t n);

10
src/fft_fr_test.c
View File

@ -48,8 +48,8 @@ void compare_sft_fft(void) {
}
// Do both fast and slow transforms
slow_ft(out0, data, 0, 1, fs.expanded_roots_of_unity, 1, fs.max_width);
fast_ft(out1, data, 0, 1, fs.expanded_roots_of_unity, 1, fs.max_width);
fft_fr_slow(out0, data, 0, 1, fs.expanded_roots_of_unity, 1, fs.max_width);
fft_fr_fast(out1, data, 0, 1, fs.expanded_roots_of_unity, 1, fs.max_width);
// Verify the results are identical
for (int i = 0; i < fs.max_width; i++) {
@ -69,8 +69,8 @@ void roundtrip_fft(void) {
}
// Forward and reverse FFT
fft(coeffs, data, &fs, false, fs.max_width);
fft(data, coeffs, &fs, true, fs.max_width);
fft_fr(coeffs, data, &fs, false, fs.max_width);
fft_fr(data, coeffs, &fs, true, fs.max_width);
// Verify that the result is still ascending values of i
for (int i = 0; i < fs.max_width; i++) {
@ -91,7 +91,7 @@ void inverse_fft(void) {
}
// Inverst FFT
fft(out, data, &fs, true, fs.max_width);
fft_fr(out, data, &fs, true, fs.max_width);
// Verify against the known result, `inv_fft_expected`
int n = sizeof(inv_fft_expected) / sizeof(inv_fft_expected[0]);