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reduce only every third multiplication

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Ahmet Inan 2024-03-26 08:59:31 +01:00
commit 10fd35cfa3
1 changed files with 6 additions and 4 deletions
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10
cauchy_reed_solomon_erasure_coding2.hh
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@ -39,12 +39,13 @@ struct CauchyReedSolomonErasureCoding2
PF col_i(i); PF col_i(i);
if (j == 0) { if (j == 0) {
PF num(1), den(1); PF num(1), den(1);
for (int k = 0; k < n; k++) { for (int k = 0, r = 2; k < n; k++, --r) {
PF col_k(k); PF col_k(k);
num = mul(num, add(rows[k], col_i)); num = mul(num, add(rows[k], col_i));
if (k != i) if (k != i)
den = mul(den, sub(col_i, col_k)); den = mul(den, sub(col_i, col_k));
if (k & 1) { if (!r) {
r = 3;
num = reduce(num); num = reduce(num);
den = reduce(den); den = reduce(den);
} }
@ -53,12 +54,13 @@ struct CauchyReedSolomonErasureCoding2
row_den = reduce(den); row_den = reduce(den);
} }
PF num(row_num), den(row_den); PF num(row_num), den(row_den);
for (int k = 0; k < n; k++) { for (int k = 0, r = 2; k < n; k++, --r) {
PF col_k(k); PF col_k(k);
num = mul(num, add(rows[j], col_k)); num = mul(num, add(rows[j], col_k));
if (k != j) if (k != j)
den = mul(den, sub(rows[j], rows[k])); den = mul(den, sub(rows[j], rows[k]));
if (k & 1) { if (!r) {
r = 3;
num = reduce(num); num = reduce(num);
den = reduce(den); den = reduce(den);
} }