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Avoid copying the accumulator twice #356

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Merged
kevlu8 merged 1 commit into from
Aug 7, 2026
Merged

Avoid copying the accumulator twice #356

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20 changes: 8 additions & 12 deletions engine/nnue/accumulator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -75,11 +75,6 @@ void AccumulatorManager::refresh_finny(Position &pos, int index) {
Accumulator &w_acc = accs[index].w_acc;
Accumulator &b_acc = accs[index].b_acc;

for (int i = 0; i < L1_SIZE; i++) {
w_acc.val[i] = f_w_acc.val[i];
b_acc.val[i] = f_b_acc.val[i];
}

for (int i = 0; i < 64; i++) {
Piece piece = pos.mailbox[i];
bool side = piece >> 3; // 1 = black, 0 = white
Expand All @@ -94,15 +89,15 @@ void AccumulatorManager::refresh_finny(Position &pos, int index) {
// Add to accumulator
int index = calculate_index((Square)i, pt, side, 0, winbucket);
for (int k = 0; k < L1_SIZE; k++) {
w_acc.val[k] += nnue_network.accumulator_weights[index][k];
f_w_acc.val[k] += nnue_network.accumulator_weights[index][k];
}
}

if (prev_w_piece != NO_PIECE) {
// Remove from accumulator
int index = calculate_index((Square)i, prev_w_pt, prev_w_side, 0, winbucket);
for (int k = 0; k < L1_SIZE; k++) {
w_acc.val[k] -= nnue_network.accumulator_weights[index][k];
f_w_acc.val[k] -= nnue_network.accumulator_weights[index][k];
}
}
}
Expand All @@ -116,26 +111,27 @@ void AccumulatorManager::refresh_finny(Position &pos, int index) {
// Add to accumulator
int index = calculate_index((Square)i, pt, side, 1, binbucket);
for (int k = 0; k < L1_SIZE; k++) {
b_acc.val[k] += nnue_network.accumulator_weights[index][k];
f_b_acc.val[k] += nnue_network.accumulator_weights[index][k];
}
}

if (prev_b_piece != NO_PIECE) {
// Remove from accumulator
int index = calculate_index((Square)i, prev_b_pt, prev_b_side, 1, binbucket);
for (int k = 0; k < L1_SIZE; k++) {
b_acc.val[k] -= nnue_network.accumulator_weights[index][k];
f_b_acc.val[k] -= nnue_network.accumulator_weights[index][k];
}
}
}
}

// Update finny tables
// Update accumulators
for (int i = 0; i < L1_SIZE; i++) {
f_w_acc.val[i] = w_acc.val[i];
f_b_acc.val[i] = b_acc.val[i];
w_acc.val[i] = f_w_acc.val[i];
b_acc.val[i] = f_b_acc.val[i];
}

// such a small loop that it's not worth incrementally doing
for (int i = 0; i < 64; i++) {
finny.mailboxes[winbucket][WHITE][i] = pos.mailbox[i];
finny.mailboxes[binbucket][BLACK][i] = pos.mailbox[i];
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