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Update Elo estimates for terms in search. #2401

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Update Elo estimates for terms in search. #2401

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42 changes: 21 additions & 21 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -784,7 +784,7 @@ namespace {
tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}

// Step 7. Razoring (~2 Elo)
// Step 7. Razoring (~0 Elo)
if ( !rootNode // The required rootNode PV handling is not available in qsearch
&& depth < 2
&& eval <= alpha - RazorMargin)
Expand All @@ -793,14 +793,14 @@ namespace {
improving = ss->staticEval >= (ss-2)->staticEval
|| (ss-2)->staticEval == VALUE_NONE;

// Step 8. Futility pruning: child node (~30 Elo)
// Step 8. Futility pruning: child node (~49 Elo)
if ( !PvNode
&& depth < 7
&& eval - futility_margin(depth, improving) >= beta
&& eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;

// Step 9. Null move search with verification search (~40 Elo)
// Step 9. Null move search with verification search (~39 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 22661
Expand Down Expand Up @@ -893,7 +893,7 @@ namespace {
}
}

// Step 11. Internal iterative deepening (~2 Elo)
// Step 11. Internal iterative deepening (~0 Elo)
if (depth >= 7 && !ttMove)
{
search<NT>(pos, ss, alpha, beta, depth - 7, cutNode);
Expand Down Expand Up @@ -955,9 +955,9 @@ namespace {
movedPiece = pos.moved_piece(move);
givesCheck = pos.gives_check(move);

// Step 13. Extensions (~70 Elo)
// Step 13. Extensions (~74 Elo)

// Singular extension search (~60 Elo). If all moves but one fail low on a
// Singular extension search (~67 Elo). If all moves but one fail low on a
// search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
// then that move is singular and should be extended. To verify this we do
// a reduced search on all the other moves but the ttMove and if the
Expand Down Expand Up @@ -1012,7 +1012,7 @@ namespace {
// Calculate new depth for this move
newDepth = depth - 1 + extension;

// Step 14. Pruning at shallow depth (~170 Elo)
// Step 14. Pruning at shallow depth (~204 Elo)
if ( !rootNode
&& pos.non_pawn_material(us)
&& bestValue > VALUE_MATED_IN_MAX_PLY)
Expand All @@ -1024,31 +1024,31 @@ namespace {
&& !givesCheck
&& (!pos.advanced_pawn_push(move) || pos.non_pawn_material(~us) > BishopValueMg))
{
// Move count based pruning
// Move count based pruning (~0 Elo)
if (moveCountPruning)
continue;

// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0);

// Countermoves based pruning (~20 Elo)
// Countermoves based pruning (~22 Elo)
if ( lmrDepth < 4 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
&& (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
&& (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
continue;

// Futility pruning: parent node (~2 Elo)
// Futility pruning: parent node (~7 Elo)
if ( lmrDepth < 6
&& !inCheck
&& ss->staticEval + 250 + 211 * lmrDepth <= alpha)
continue;

// Prune moves with negative SEE (~10 Elo)
// Prune moves with negative SEE (~17 Elo)
if (!pos.see_ge(move, Value(-(31 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
continue;
}
else if ( !(givesCheck && extension)
&& !pos.see_ge(move, Value(-199) * depth)) // (~20 Elo)
&& !pos.see_ge(move, Value(-199) * depth)) // (~26 Elo)
continue;
}

Expand All @@ -1072,7 +1072,7 @@ namespace {
// Step 15. Make the move
pos.do_move(move, st, givesCheck);

// Step 16. Reduced depth search (LMR). If the move fails high it will be
// Step 16. Reduced depth search (LMR, ~208 Elo). If the move fails high it will be
// re-searched at full depth.
if ( depth >= 3
&& moveCount > 1 + 2 * rootNode
Expand All @@ -1088,31 +1088,31 @@ namespace {
if (th.marked())
r++;

// Decrease reduction if position is or has been on the PV
// Decrease reduction if position is or has been on the PV (~8 Elo)
if (ttPv)
r -= 2;

// Decrease reduction if opponent's move count is high (~10 Elo)
// Decrease reduction if opponent's move count is high (~4 Elo)
if ((ss-1)->moveCount > 15)
r--;

// Decrease reduction if ttMove has been singularly extended
// Decrease reduction if ttMove has been singularly extended (~3 Elo)
if (singularLMR)
r -= 2;

if (!captureOrPromotion)
{
// Increase reduction if ttMove is a capture (~0 Elo)
// Increase reduction if ttMove is a capture (~4 Elo)
if (ttCapture)
r++;

// Increase reduction for cut nodes (~5 Elo)
// Increase reduction for cut nodes (~10 Elo)
if (cutNode)
r += 2;

// Decrease reduction for moves that escape a capture. Filter out
// castling moves, because they are coded as "king captures rook" and
// hence break make_move(). (~5 Elo)
// hence break make_move(). (~2 Elo)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(reverse_move(move)))
r -= 2;
Expand All @@ -1130,14 +1130,14 @@ namespace {
&& thisThread->mainHistory[us][from_to(move)] >= 0)
ss->statScore = 0;

// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
// Decrease/increase reduction by comparing opponent's stat score (~8 Elo)
if (ss->statScore >= -99 && (ss-1)->statScore < -116)
r--;

else if ((ss-1)->statScore >= -117 && ss->statScore < -144)
r++;

// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
// Decrease/increase reduction for moves with a good/bad history (~26 Elo)
r -= ss->statScore / 16384;
}

Expand Down