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Merge bitcoin-core/secp256k1#1761: ecmult_multi: reduce strauss memory usage by 30%

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26166c4f5f ecmult_multi: reduce strauss memory usage by 30% (Jonas Nick)

Pull request description:

  This is a draft because I'm not sure about the cleanest way to implement it.

ACKs for top commit:
  real-or-random:
    ACK 26166c4f5f benchmarks show no significant difference (only tried low point counts)
  siv2r:
    tACK 26166c4
  hebasto:
    ACK 26166c4f5f, I have reviewed the code and it looks OK.

Tree-SHA512: f289daee0b0b51451331eefdd99200a78bd83539365d38465c038dc0e6ad940daf821119f7161b08a2390cf046e3859a8f950f2fe881a427aba16353031def7d
This commit is contained in:
merge-script
2025-11-18 09:36:40 +01:00
parent c8206b1ce6 26166c4f5f
commit b6c2a3cd77
1 changed files with 19 additions and 4 deletions
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23
src/ecmult_impl.h
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@@ -220,9 +220,24 @@ static int secp256k1_ecmult_wnaf(int *wnaf, int len, const secp256k1_scalar *a,
return last_set_bit + 1; return last_set_bit + 1;
} }
/* Same as secp256k1_ecmult_wnaf, but stores to int8_t array. Requires w <= 8. */
static int secp256k1_ecmult_wnaf_small(int8_t *wnaf, int len, const secp256k1_scalar *a, int w) {
int wnaf_tmp[256];
int ret, i;
VERIFY_CHECK(2 <= w && w <= 8);
ret = secp256k1_ecmult_wnaf(wnaf_tmp, len, a, w);
for (i = 0; i < len; i++) {
wnaf[i] = (int8_t)wnaf_tmp[i];
}
return ret;
}
struct secp256k1_strauss_point_state { struct secp256k1_strauss_point_state {
int wnaf_na_1[129]; int8_t wnaf_na_1[129];
int wnaf_na_lam[129]; int8_t wnaf_na_lam[129];
int bits_na_1; int bits_na_1;
int bits_na_lam; int bits_na_lam;
}; };
@@ -259,8 +274,8 @@ static void secp256k1_ecmult_strauss_wnaf(const struct secp256k1_strauss_state *
secp256k1_scalar_split_lambda(&na_1, &na_lam, &na[np]); secp256k1_scalar_split_lambda(&na_1, &na_lam, &na[np]);
/* build wnaf representation for na_1 and na_lam. */ /* build wnaf representation for na_1 and na_lam. */
state->ps[no].bits_na_1 = secp256k1_ecmult_wnaf(state->ps[no].wnaf_na_1, 129, &na_1, WINDOW_A); state->ps[no].bits_na_1 = secp256k1_ecmult_wnaf_small(state->ps[no].wnaf_na_1, 129, &na_1, WINDOW_A);
state->ps[no].bits_na_lam = secp256k1_ecmult_wnaf(state->ps[no].wnaf_na_lam, 129, &na_lam, WINDOW_A); state->ps[no].bits_na_lam = secp256k1_ecmult_wnaf_small(state->ps[no].wnaf_na_lam, 129, &na_lam, WINDOW_A);
VERIFY_CHECK(state->ps[no].bits_na_1 <= 129); VERIFY_CHECK(state->ps[no].bits_na_1 <= 129);
VERIFY_CHECK(state->ps[no].bits_na_lam <= 129); VERIFY_CHECK(state->ps[no].bits_na_lam <= 129);
if (state->ps[no].bits_na_1 > bits) { if (state->ps[no].bits_na_1 > bits) {