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Merge pull request #466 from jtraglia/fft-file
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Move FFT functions to fft.{c,h} files
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@asn-d6
asn-d6 authored Aug 5, 2024
2 parents 387685e + 7fe30c8 commit 4db29c6
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Showing 11 changed files with 247 additions and 189 deletions.
2 changes: 2 additions & 0 deletions bindings/node.js/Makefile
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Expand Up @@ -36,12 +36,14 @@ build: install clean
@cp ../../src/common.c deps/c-kzg
@cp ../../src/eip4844.c deps/c-kzg
@cp ../../src/eip7594.c deps/c-kzg
@cp ../../src/fft.c deps/c-kzg
@cp ../../src/setup.c deps/c-kzg
@# Copy header files
@cp ../../src/ckzg.h deps/c-kzg
@cp ../../src/common.h deps/c-kzg
@cp ../../src/eip4844.h deps/c-kzg
@cp ../../src/eip7594.h deps/c-kzg
@cp ../../src/fft.h deps/c-kzg
@cp ../../src/setup.h deps/c-kzg
@# Copy trusted setup
@cp ../../src/trusted_setup.txt deps/c-kzg
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1 change: 1 addition & 0 deletions src/ckzg.c
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Expand Up @@ -17,4 +17,5 @@
#include "common.c"
#include "eip4844.c"
#include "eip7594.c"
#include "fft.c"
#include "setup.c"
93 changes: 0 additions & 93 deletions src/common.c
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Expand Up @@ -608,96 +608,3 @@ C_KZG_RET g1_lincomb_fast(g1_t *out, const g1_t *p, const fr_t *coeffs, size_t l
c_kzg_free(scalars);
return ret;
}

/**
* Fast Fourier Transform.
*
* Recursively divide and conquer.
*
* @param[out] out The results (length `n`)
* @param[in] in The input data (length `n * stride`)
* @param[in] stride The input data stride
* @param[in] roots Roots of unity (length `n * roots_stride`)
* @param[in] roots_stride The stride interval among the roots of unity
* @param[in] n Length of the FFT, must be a power of two
*/
static void g1_fft_fast(
g1_t *out, const g1_t *in, uint64_t stride, const fr_t *roots, uint64_t roots_stride, uint64_t n
) {
g1_t y_times_root;
uint64_t half = n / 2;
if (half > 0) { /* Tunable parameter */
g1_fft_fast(out, in, stride * 2, roots, roots_stride * 2, half);
g1_fft_fast(out + half, in + stride, stride * 2, roots, roots_stride * 2, half);
for (uint64_t i = 0; i < half; i++) {
/* If the point is infinity, we can skip the calculation */
if (blst_p1_is_inf(&out[i + half])) {
out[i + half] = out[i];
} else {
/* If the scalar is one, we can skip the multiplication */
if (fr_is_one(&roots[i * roots_stride])) {
y_times_root = out[i + half];
} else {
g1_mul(&y_times_root, &out[i + half], &roots[i * roots_stride]);
}
g1_sub(&out[i + half], &out[i], &y_times_root);
blst_p1_add_or_double(&out[i], &out[i], &y_times_root);
}
}
} else {
*out = *in;
}
}

/**
* The entry point for forward FFT over G1 points.
*
* @param[out] out The results (array of length n)
* @param[in] in The input data (array of length n)
* @param[in] n Length of the arrays
* @param[in] s The trusted setup
*
* @remark The array lengths must be a power of two.
* @remark Use g1_ifft() for inverse transformation.
*/
C_KZG_RET g1_fft(g1_t *out, const g1_t *in, size_t n, const KZGSettings *s) {
/* Ensure the length is valid */
if (n > FIELD_ELEMENTS_PER_EXT_BLOB || !is_power_of_two(n)) {
return C_KZG_BADARGS;
}

uint64_t stride = FIELD_ELEMENTS_PER_EXT_BLOB / n;
g1_fft_fast(out, in, 1, s->roots_of_unity, stride, n);

return C_KZG_OK;
}

/**
* The entry point for inverse FFT over G1 points.
*
* @param[out] out The results (array of length n)
* @param[in] in The input data (array of length n)
* @param[in] n Length of the arrays
* @param[in] s The trusted setup
*
* @remark The array lengths must be a power of two.
* @remark Use g1_fft() for forward transformation.
*/
C_KZG_RET g1_ifft(g1_t *out, const g1_t *in, size_t n, const KZGSettings *s) {
/* Ensure the length is valid */
if (n > FIELD_ELEMENTS_PER_EXT_BLOB || !is_power_of_two(n)) {
return C_KZG_BADARGS;
}

uint64_t stride = FIELD_ELEMENTS_PER_EXT_BLOB / n;
g1_fft_fast(out, in, 1, s->reverse_roots_of_unity, stride, n);

fr_t inv_len;
fr_from_uint64(&inv_len, n);
blst_fr_eucl_inverse(&inv_len, &inv_len);
for (uint64_t i = 0; i < n; i++) {
g1_mul(&out[i], &out[i], &inv_len);
}

return C_KZG_OK;
}
3 changes: 1 addition & 2 deletions src/common.h
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Expand Up @@ -17,6 +17,7 @@
#pragma once

#include "blst.h"

#include <stdbool.h>

#ifdef __cplusplus
Expand Down Expand Up @@ -276,8 +277,6 @@ void g1_mul(g1_t *out, const g1_t *a, const fr_t *b);
bool pairings_verify(const g1_t *a1, const g2_t *a2, const g1_t *b1, const g2_t *b2);
void g1_lincomb_naive(g1_t *out, const g1_t *p, const fr_t *coeffs, uint64_t len);
C_KZG_RET g1_lincomb_fast(g1_t *out, const g1_t *p, const fr_t *coeffs, size_t len);
C_KZG_RET g1_fft(g1_t *out, const g1_t *in, size_t n, const KZGSettings *s);
C_KZG_RET g1_ifft(g1_t *out, const g1_t *in, size_t n, const KZGSettings *s);

#ifdef __cplusplus
}
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87 changes: 1 addition & 86 deletions src/eip7594.c
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Expand Up @@ -18,6 +18,7 @@

#include "blst.h"
#include "common.h"
#include "fft.h"

#include <assert.h> /* For assert */
#include <stdlib.h> /* For NULL */
Expand Down Expand Up @@ -108,92 +109,6 @@ static uint32_t reverse_bits_limited(uint32_t n, uint32_t value) {
return reverse_bits(value) >> unused_bit_len;
}

////////////////////////////////////////////////////////////////////////////////////////////////////
// Fast Fourier Transform
////////////////////////////////////////////////////////////////////////////////////////////////////

/**
* Fast Fourier Transform.
*
* Recursively divide and conquer.
*
* @param[out] out The results (length `n`)
* @param[in] in The input data (length `n * stride`)
* @param[in] stride The input data stride
* @param[in] roots Roots of unity (length `n * roots_stride`)
* @param[in] roots_stride The stride interval among the roots of unity
* @param[in] n Length of the FFT, must be a power of two
*/
static void fr_fft_fast(
fr_t *out, const fr_t *in, size_t stride, const fr_t *roots, size_t roots_stride, size_t n
) {
size_t half = n / 2;
if (half > 0) {
fr_t y_times_root;
fr_fft_fast(out, in, stride * 2, roots, roots_stride * 2, half);
fr_fft_fast(out + half, in + stride, stride * 2, roots, roots_stride * 2, half);
for (size_t i = 0; i < half; i++) {
blst_fr_mul(&y_times_root, &out[i + half], &roots[i * roots_stride]);
blst_fr_sub(&out[i + half], &out[i], &y_times_root);
blst_fr_add(&out[i], &out[i], &y_times_root);
}
} else {
*out = *in;
}
}

/**
* The entry point for forward FFT over field elements.
*
* @param[out] out The results (array of length n)
* @param[in] in The input data (array of length n)
* @param[in] n Length of the arrays
* @param[in] s The trusted setup
*
* @remark The array lengths must be a power of two.
* @remark Use fr_ifft() for inverse transformation.
*/
static C_KZG_RET fr_fft(fr_t *out, const fr_t *in, size_t n, const KZGSettings *s) {
/* Ensure the length is valid */
if (n > FIELD_ELEMENTS_PER_EXT_BLOB || !is_power_of_two(n)) {
return C_KZG_BADARGS;
}

size_t stride = FIELD_ELEMENTS_PER_EXT_BLOB / n;
fr_fft_fast(out, in, 1, s->roots_of_unity, stride, n);

return C_KZG_OK;
}

/**
* The entry point for inverse FFT over field elements.
*
* @param[out] out The results (array of length n)
* @param[in] in The input data (array of length n)
* @param[in] n Length of the arrays
* @param[in] s The trusted setup
*
* @remark The array lengths must be a power of two.
* @remark Use fr_fft() for forward transformation.
*/
static C_KZG_RET fr_ifft(fr_t *out, const fr_t *in, size_t n, const KZGSettings *s) {
/* Ensure the length is valid */
if (n > FIELD_ELEMENTS_PER_EXT_BLOB || !is_power_of_two(n)) {
return C_KZG_BADARGS;
}

size_t stride = FIELD_ELEMENTS_PER_EXT_BLOB / n;
fr_fft_fast(out, in, 1, s->reverse_roots_of_unity, stride, n);

fr_t inv_len;
fr_from_uint64(&inv_len, n);
blst_fr_inverse(&inv_len, &inv_len);
for (size_t i = 0; i < n; i++) {
blst_fr_mul(&out[i], &out[i], &inv_len);
}
return C_KZG_OK;
}

////////////////////////////////////////////////////////////////////////////////////////////////////
// Vanishing Polynomial
////////////////////////////////////////////////////////////////////////////////////////////////////
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4 changes: 2 additions & 2 deletions src/eip7594.h
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Expand Up @@ -16,10 +16,10 @@

#pragma once

#include <stdint.h>

#include "common.h"

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif
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