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Optimization: avoid unnecessary doublings in precomputation

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This commit is contained in:
Peter Dettman
2021-12-26 22:50:09 -05:00
committed by Pieter Wuille
parent 15d0cca2a6
commit 6247f485b6
1 changed files with 6 additions and 4 deletions
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10
src/ecmult_gen_compute_table_impl.h
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@@ -54,16 +54,18 @@ static void secp256k1_ecmult_gen_compute_table(secp256k1_ge_storage* table, cons
secp256k1_gej_set_infinity(&sum);
for (tooth = 0; tooth < teeth; ++tooth) {
/* Here u = 2^((block*teeth + tooth)*spacing) * gen/2. */
int bit_off;
/* Make sum = sum(2^((block*teeth + t)*spacing), t=0..tooth) * gen/2. */
secp256k1_gej_add_var(&sum, &sum, &u, NULL);
/* Make u = 2^((block*teeth + tooth)*spacing + 1) * gen/2. */
secp256k1_gej_double_var(&u, &u, NULL);
/* Make ds[tooth] = u = 2^((block*teeth + tooth)*spacing + 1) * gen/2. */
ds[tooth] = u;
/* Make u = 2^((block*teeth + tooth + 1)*spacing) * gen/2. */
for (bit_off = 1; bit_off < spacing; ++bit_off) {
secp256k1_gej_double_var(&u, &u, NULL);
/* Make u = 2^((block*teeth + tooth + 1)*spacing) * gen/2, unless at the end. */
if (block + tooth != blocks + teeth - 2) {
int bit_off;
for (bit_off = 1; bit_off < spacing; ++bit_off) {
secp256k1_gej_double_var(&u, &u, NULL);
}
}
}
/* Now u = 2^((block*teeth + teeth)*spacing) * gen/2