Remove formerPV variable.

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c69b240836e68e129c7bfc8f4542214eaa8d4af5..2c7c6fd671c55e6d9277ca675077f7b4debde2ef 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -253,7 +253,7 @@ void Thread::search() {
   // To allow access to (ss-7) up to (ss+2), the stack must be oversized.
   // The former is needed to allow update_continuation_histories(ss-1, ...),
   // which accesses its argument at ss-6, also near the root.
-  // The latter is needed for statScores and killer initialization.
+  // The latter is needed for statScore and killer initialization.
   Stack stack[MAX_PLY+10], *ss = stack+7;
   Move  pv[MAX_PLY+1];
   Value bestValue, alpha, beta, delta;
@@ -268,6 +268,9 @@ void Thread::search() {
   for (int i = 7; i > 0; i--)
       (ss-i)->continuationHistory = &this->continuationHistory[0][0][NO_PIECE][0]; // Use as a sentinel
 
+  for (int i = 0; i <= MAX_PLY + 2; ++i)
+      (ss+i)->ply = i;
+
   ss->pv = pv;
 
   bestValue = delta = alpha = -VALUE_INFINITE;
@@ -561,7 +564,7 @@ namespace {
     Move ttMove, move, excludedMove, bestMove;
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
-    bool formerPv, givesCheck, improving, didLMR, priorCapture;
+    bool givesCheck, improving, didLMR, priorCapture;
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
          ttCapture, singularQuietLMR;
     Piece movedPiece;
@@ -607,7 +610,6 @@ namespace {
 
     assert(0 <= ss->ply && ss->ply < MAX_PLY);
 
-    (ss+1)->ply = ss->ply + 1;
     (ss+1)->ttPv = false;
     (ss+1)->excludedMove = bestMove = MOVE_NONE;
     (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
@@ -632,7 +634,6 @@ namespace {
             : ss->ttHit    ? tte->move() : MOVE_NONE;
     if (!excludedMove)
         ss->ttPv = PvNode || (ss->ttHit && tte->is_pv());
-    formerPv = ss->ttPv && !PvNode;
 
     // Update low ply history for previous move if we are near root and position is or has been in PV
     if (   ss->ttPv
@@ -1062,8 +1063,8 @@ moves_loop: // When in check, search starts from here
           && (tte->bound() & BOUND_LOWER)
           &&  tte->depth() >= depth - 3)
       {
-          Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2;
-          Depth singularDepth = (depth - 1 + 3 * formerPv) / 2;
+          Value singularBeta = ttValue - 2 * depth;
+          Depth singularDepth = (depth - 1) / 2;
 
           ss->excludedMove = move;
           value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
@@ -1097,6 +1098,10 @@ moves_loop: // When in check, search starts from here
                   return beta;
           }
       }
+      else if (   givesCheck
+               && depth > 6
+               && abs(ss->staticEval) > Value(100))
+          extension = 1;
 
       // Add extension to new depth
       newDepth += extension;
@@ -1121,8 +1126,8 @@ moves_loop: // When in check, search starts from here
       if (    depth >= 3
           &&  moveCount > 1 + 2 * rootNode
           && (  !captureOrPromotion
-              || cutNode
-              || (!PvNode && !formerPv))
+              || (cutNode && (ss-1)->moveCount > 1)
+              || !ss->ttPv)
           && (!PvNode || ss->ply > 1 || thisThread->id() % 4 != 3))
       {
           Depth r = reduction(improving, depth, moveCount);
@@ -1273,7 +1278,6 @@ moves_loop: // When in check, search starts from here
               else
               {
                   assert(value >= beta); // Fail high
-                  ss->statScore = 0;
                   break;
               }
           }
@@ -1376,7 +1380,6 @@ moves_loop: // When in check, search starts from here
     }
 
     Thread* thisThread = pos.this_thread();
-    (ss+1)->ply = ss->ply + 1;
     bestMove = MOVE_NONE;
     ss->inCheck = pos.checkers();
     moveCount = 0;