X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=eb30d9fac8cd50c9cfc72ec1309e30a014579376;hb=fbc7a328c67092799547f93e684323e2c1a6226e;hp=abc6874e99583360a679ffe1cdad8806fee34861;hpb=6ecab03dee15fe30bc0237919180a2e51e0ce4b1;p=stockfish

diff --git a/src/search.cpp b/src/search.cpp
index abc6874e..eb30d9fa 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -280,7 +280,7 @@ void MainThread::search() {
       std::map<Move, int64_t> votes;
       Value minScore = this->rootMoves[0].score;
 
-      // Find out minimum score
+      // Find minimum score
       for (Thread* th: Threads)
           minScore = std::min(minScore, th->rootMoves[0].score);
 
@@ -290,14 +290,15 @@ void MainThread::search() {
           votes[th->rootMoves[0].pv[0]] +=
               (th->rootMoves[0].score - minScore + 14) * int(th->completedDepth);
 
-          if (bestThread->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY)
+          if (abs(bestThread->rootMoves[0].score) >= VALUE_TB_WIN_IN_MAX_PLY)
           {
-              // Make sure we pick the shortest mate
+              // Make sure we pick the shortest mate / TB conversion or stave off mate the longest
               if (th->rootMoves[0].score > bestThread->rootMoves[0].score)
                   bestThread = th;
           }
           else if (   th->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY
-                   || votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]])
+                   || (   th->rootMoves[0].score > VALUE_TB_LOSS_IN_MAX_PLY
+                       && votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]]))
               bestThread = th;
       }
   }
@@ -433,7 +434,7 @@ void Thread::search() {
           if (rootDepth >= 4)
           {
               Value previousScore = rootMoves[pvIdx].previousScore;
-              delta = Value(21 + abs(previousScore) / 256);
+              delta = Value(21);
               alpha = std::max(previousScore - delta,-VALUE_INFINITE);
               beta  = std::min(previousScore + delta, VALUE_INFINITE);
 
@@ -867,7 +868,7 @@ namespace {
 
         if (nullValue >= beta)
         {
-            // Do not return unproven mate scores
+            // Do not return unproven mate or TB scores
             if (nullValue >= VALUE_TB_WIN_IN_MAX_PLY)
                 nullValue = beta;
 
@@ -962,6 +963,7 @@ moves_loop: // When in check, search starts from here
     value = bestValue;
     singularLMR = moveCountPruning = false;
     ttCapture = ttMove && pos.capture_or_promotion(ttMove);
+    bool formerPv = ttPv && !PvNode;
 
     // Mark this node as being searched
     ThreadHolding th(thisThread, posKey, ss->ply);
@@ -1054,8 +1056,8 @@ moves_loop: // When in check, search starts from here
           &&  tte->depth() >= depth - 3
           &&  pos.legal(move))
       {
-          Value singularBeta = ttValue - (((ttPv && !PvNode) + 4) * depth) / 2;
-          Depth singularDepth = (depth - 1 + 3 * (ttPv && !PvNode)) / 2;
+          Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2;
+          Depth singularDepth = (depth - 1 + 3 * formerPv) / 2;
           ss->excludedMove = move;
           value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
           ss->excludedMove = MOVE_NONE;
@@ -1143,13 +1145,16 @@ moves_loop: // When in check, search starts from here
           if (ttPv)
               r -= 2;
 
+          if (moveCountPruning && !formerPv)
+              r++;
+
           // Decrease reduction if opponent's move count is high (~5 Elo)
           if ((ss-1)->moveCount > 14)
               r--;
 
           // Decrease reduction if ttMove has been singularly extended (~3 Elo)
           if (singularLMR)
-              r -= 1 + (ttPv && !PvNode);
+              r -= 1 + formerPv;
 
           if (!captureOrPromotion)
           {
@@ -1182,12 +1187,19 @@ moves_loop: // When in check, search starts from here
                   r++;
 
               // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
-              r -= ss->statScore / 16384;
+              r -= ss->statScore / 16434;
+          }
+          else
+          {
+            // Increase reduction for captures/promotions if late move and at low depth
+            if (depth < 8 && moveCount > 2)
+                r++;
+
+            // Unless giving check, this capture is likely bad
+            if (   !givesCheck
+                && ss->staticEval + PieceValue[EG][pos.captured_piece()] + 200 * depth <= alpha)
+                r++;
           }
-
-          // Increase reduction for captures/promotions if late move and at low depth
-          else if (depth < 8 && moveCount > 2)
-              r++;
 
           Depth d = Utility::clamp(newDepth - r, 1, newDepth);