Increase pruning if evaluation is not improving

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c6bc8e372bcd28d4c02c8b2a6ccd1b22a3e4a6e8..78a72beccfdc777e549a7dd786d8483208089b9f 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -66,7 +66,7 @@ namespace {
 
   // Futility lookup tables (initialized at startup) and their access functions
   Value FutilityMargins[16][64]; // [depth][moveNumber]
-  int FutilityMoveCounts[32];    // [depth]
+  int FutilityMoveCounts[2][32]; // [improving][depth]
 
   inline Value futility_margin(Depth d, int mn) {
 
@@ -146,7 +146,11 @@ void Search::init() {
 
   // Init futility move count array
   for (d = 0; d < 32; d++)
-      FutilityMoveCounts[d] = int(3.001 + 0.3 * pow(double(d), 1.8));
+  {
+      FutilityMoveCounts[1][d] = int(3.001 + 0.3 * pow(double(d), 1.8));
+      FutilityMoveCounts[0][d] = d < 5 ? FutilityMoveCounts[1][d]
+                                       : 3 * FutilityMoveCounts[1][d] / 4;
+  }
 }
 
 
@@ -294,11 +298,11 @@ namespace {
 
   void id_loop(Position& pos) {
 
-    Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1)
+    Stack stack[MAX_PLY_PLUS_3], *ss = stack+2; // To allow referencing (ss-2)
     int depth, prevBestMoveChanges;
     Value bestValue, alpha, beta, delta;
 
-    std::memset(ss-1, 0, 4 * sizeof(Stack));
+    std::memset(ss-2, 0, 5 * sizeof(Stack));
     (ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains
 
     depth = BestMoveChanges = 0;
@@ -496,7 +500,7 @@ namespace {
     Depth ext, newDepth;
     Value bestValue, value, ttValue;
     Value eval, nullValue, futilityValue;
-    bool inCheck, givesCheck, pvMove, singularExtensionNode;
+    bool inCheck, givesCheck, pvMove, singularExtensionNode, improving;
     bool captureOrPromotion, dangerous, doFullDepthSearch;
     int moveCount, quietCount;
 
@@ -765,6 +769,7 @@ moves_loop: // When in check and at SpNode search starts from here
     MovePicker mp(pos, ttMove, depth, History, countermoves, ss);
     CheckInfo ci(pos);
     value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
+    improving = ss->staticEval >= (ss-2)->staticEval;
     singularExtensionNode =   !RootNode
                            && !SpNode
                            &&  depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY)
@@ -861,7 +866,7 @@ moves_loop: // When in check and at SpNode search starts from here
       {
           // Move count based pruning
           if (   depth < 16 * ONE_PLY
-              && moveCount >= FutilityMoveCounts[depth]
+              && moveCount >= FutilityMoveCounts[improving][depth]
               && (!threatMove || !refutes(pos, move, threatMove)))
           {
               if (SpNode)
@@ -1562,7 +1567,7 @@ moves_loop: // When in check and at SpNode search starts from here
 
 void RootMove::extract_pv_from_tt(Position& pos) {
 
-  StateInfo state[MAX_PLY_PLUS_2], *st = state;
+  StateInfo state[MAX_PLY_PLUS_3], *st = state;
   const TTEntry* tte;
   int ply = 0;
   Move m = pv[0];
@@ -1595,7 +1600,7 @@ void RootMove::extract_pv_from_tt(Position& pos) {
 
 void RootMove::insert_pv_in_tt(Position& pos) {
 
-  StateInfo state[MAX_PLY_PLUS_2], *st = state;
+  StateInfo state[MAX_PLY_PLUS_3], *st = state;
   const TTEntry* tte;
   int ply = 0;
 
@@ -1670,10 +1675,10 @@ void Thread::idle_loop() {
 
           Threads.mutex.unlock();
 
-          Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1)
+          Stack stack[MAX_PLY_PLUS_3], *ss = stack+2; // To allow referencing (ss-2)
           Position pos(*sp->pos, this);
 
-          std::memcpy(ss-1, sp->ss-1, 4 * sizeof(Stack));
+          std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack));
           ss->splitPoint = sp;
 
           sp->mutex.lock();