Tweak reductions formula: 0.88 * depth + 0.12

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 97ad9912b6b38e21c890e462f30cca55efbacba5..89636f23575398840559967029541bf94ad3d736 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -153,7 +153,8 @@ void Search::init() {
       for (int d = 1; d < 64; ++d)
           for (int mc = 1; mc < 64; ++mc)
           {
-              double r = log(d) * log(mc) / 1.95;
+              double slope = d > 2 ? 0.88 * d + 0.36 : d;
+              double r = log(slope) * log(mc) / 1.95;
 
               Reductions[NonPV][imp][d][mc] = int(std::round(r));
               Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);
@@ -290,7 +291,7 @@ void Thread::search() {
 
   std::memset(ss-4, 0, 7 * sizeof(Stack));
   for (int i = 4; i > 0; i--)
-     (ss-i)->contHistory = this->contHistory[NO_PIECE][0].get(); // Use as sentinel
+     (ss-i)->continuationHistory = this->continuationHistory[NO_PIECE][0].get(); // Use as sentinel
 
   bestValue = delta = alpha = -VALUE_INFINITE;
   beta = VALUE_INFINITE;
@@ -331,7 +332,7 @@ void Thread::search() {
       if (idx > 0)
       {
           int i = (idx - 1) % 20;
-          if (((rootDepth / ONE_PLY + rootPos.game_ply() + SkipPhase[i]) / SkipSize[i]) % 2)
+          if (((rootDepth / ONE_PLY + SkipPhase[i]) / SkipSize[i]) % 2)
               continue;  // Retry with an incremented rootDepth
       }
 
@@ -587,7 +588,7 @@ namespace {
 
     (ss+1)->ply = ss->ply + 1;
     ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
-    ss->contHistory = thisThread->contHistory[NO_PIECE][0].get();
+    ss->continuationHistory = thisThread->continuationHistory[NO_PIECE][0].get();
     (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
     Square prevSq = to_sq((ss-1)->currentMove);
 
@@ -751,7 +752,7 @@ namespace {
         Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
 
         ss->currentMove = MOVE_NULL;
-        ss->contHistory = thisThread->contHistory[NO_PIECE][0].get();
+        ss->continuationHistory = thisThread->continuationHistory[NO_PIECE][0].get();
 
         pos.do_null_move(st);
 
@@ -802,7 +803,7 @@ namespace {
                 probCutCount++;
 
                 ss->currentMove = move;
-                ss->contHistory = thisThread->contHistory[pos.moved_piece(move)][to_sq(move)].get();
+                ss->continuationHistory = thisThread->continuationHistory[pos.moved_piece(move)][to_sq(move)].get();
 
                 assert(depth >= 5 * ONE_PLY);
 
@@ -835,7 +836,7 @@ namespace {
 
 moves_loop: // When in check, search starts from here
 
-    const PieceToHistory* contHist[] = { (ss-1)->contHistory, (ss-2)->contHistory, nullptr, (ss-4)->contHistory };
+    const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, nullptr, (ss-4)->continuationHistory };
     Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
 
     MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
@@ -970,7 +971,7 @@ moves_loop: // When in check, search starts from here
 
       // Update the current move (this must be done after singular extension search)
       ss->currentMove = move;
-      ss->contHistory = thisThread->contHistory[movedPiece][to_sq(move)].get();
+      ss->continuationHistory = thisThread->continuationHistory[movedPiece][to_sq(move)].get();
 
       // Step 15. Make the move
       pos.do_move(move, st, givesCheck);
@@ -985,11 +986,9 @@ moves_loop: // When in check, search starts from here
 
           if (captureOrPromotion) // (~5 Elo)
           {
-              // Increase reduction by comparing opponent's stat score
-              if ((ss-1)->statScore >= 0)
-                  r += ONE_PLY;
-
-              r -= r ? ONE_PLY : DEPTH_ZERO;
+              // Decrease reduction by comparing opponent's stat score
+              if ((ss-1)->statScore < 0)
+                  r -= ONE_PLY;
           }
           else
           {
@@ -1030,10 +1029,10 @@ moves_loop: // When in check, search starts from here
                   r += ONE_PLY;
 
               // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
-              r = std::max(DEPTH_ZERO, (r / ONE_PLY - ss->statScore / 20000) * ONE_PLY);
+              r -= ss->statScore / 20000 * ONE_PLY;
           }
 
-          Depth d = std::max(newDepth - r, ONE_PLY);
+          Depth d = std::max(newDepth - std::max(r, DEPTH_ZERO), ONE_PLY);
 
           value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
 
@@ -1212,8 +1211,10 @@ moves_loop: // When in check, search starts from here
         ss->pv[0] = MOVE_NONE;
     }
 
+    Thread* thisThread = pos.this_thread();
     (ss+1)->ply = ss->ply + 1;
     ss->currentMove = bestMove = MOVE_NONE;
+    ss->continuationHistory = thisThread->continuationHistory[NO_PIECE][0].get();
     inCheck = pos.checkers();
     moveCount = 0;
 
@@ -1239,8 +1240,8 @@ moves_loop: // When in check, search starts from here
         && ttHit
         && tte->depth() >= ttDepth
         && ttValue != VALUE_NONE // Only in case of TT access race
-        && (ttValue >= beta ? (tte->bound() &  BOUND_LOWER)
-                            : (tte->bound() &  BOUND_UPPER)))
+        && (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
+                            : (tte->bound() & BOUND_UPPER)))
         return ttValue;
 
     // Evaluate the position statically
@@ -1258,7 +1259,7 @@ moves_loop: // When in check, search starts from here
                 ss->staticEval = bestValue = evaluate(pos);
 
             // Can ttValue be used as a better position evaluation?
-            if (   ttValue != VALUE_NONE
+            if (    ttValue != VALUE_NONE
                 && (tte->bound() & (ttValue > bestValue ? BOUND_LOWER : BOUND_UPPER)))
                 bestValue = ttValue;
         }
@@ -1283,12 +1284,15 @@ moves_loop: // When in check, search starts from here
         futilityBase = bestValue + 128;
     }
 
+    const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, nullptr, (ss-4)->continuationHistory };
+
     // Initialize a MovePicker object for the current position, and prepare
     // to search the moves. Because the depth is <= 0 here, only captures,
     // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
     // be generated.
-    MovePicker mp(pos, ttMove, depth, &pos.this_thread()->mainHistory,
-                                      &pos.this_thread()->captureHistory,
+    MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
+                                      &thisThread->captureHistory,
+                                      contHist,
                                       to_sq((ss-1)->currentMove));
 
     // Loop through the moves until no moves remain or a beta cutoff occurs
@@ -1345,6 +1349,7 @@ moves_loop: // When in check, search starts from here
       }
 
       ss->currentMove = move;
+      ss->continuationHistory = thisThread->continuationHistory[pos.moved_piece(move)][to_sq(move)].get();
 
       // Make and search the move
       pos.do_move(move, st, givesCheck);
@@ -1436,7 +1441,7 @@ moves_loop: // When in check, search starts from here
 
     for (int i : {1, 2, 4})
         if (is_ok((ss-i)->currentMove))
-            (*(ss-i)->contHistory)[pc][to] << bonus;
+            (*(ss-i)->continuationHistory)[pc][to] << bonus;
   }