Time management: move faster if PV is stable

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index bba0cb6593c2944cf0dccf2e20a3f43ca1850fa7..dcd8b0d16597510d0067899cec7602c38dc93226 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -84,7 +84,7 @@ namespace {
 
   size_t PVSize, PVIdx;
   TimeManager TimeMgr;
-  int BestMoveChanges;
+  float BestMoveChanges;
   Value DrawValue[COLOR_NB];
   HistoryStats History;
   GainsStats Gains;
@@ -153,9 +153,8 @@ void Search::init() {
   // Init futility move count array
   for (d = 0; d < 32; d++)
   {
-      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;
+      FutilityMoveCounts[0][d] = int(3.001 + 0.3 * pow(double(d       ), 1.8)) * (d < 5 ? 4 : 3) / 4;
+      FutilityMoveCounts[1][d] = int(3.001 + 0.3 * pow(double(d + 0.98), 1.8));
   }
 }
 
@@ -304,14 +303,15 @@ namespace {
 
   void id_loop(Position& pos) {
 
-    Stack stack[MAX_PLY_PLUS_3], *ss = stack+2; // To allow referencing (ss-2)
-    int depth, prevBestMoveChanges;
+    Stack stack[MAX_PLY_PLUS_6], *ss = stack+2; // To allow referencing (ss-2)
+    int depth;
     Value bestValue, alpha, beta, delta;
 
     std::memset(ss-2, 0, 5 * sizeof(Stack));
     (ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains
 
-    depth = BestMoveChanges = 0;
+    depth = 0;
+    BestMoveChanges = 0;
     bestValue = delta = alpha = -VALUE_INFINITE;
     beta = VALUE_INFINITE;
 
@@ -333,14 +333,14 @@ namespace {
     // Iterative deepening loop until requested to stop or target depth reached
     while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
     {
+        // Age out PV variability metric
+        BestMoveChanges *= 0.8;
+
         // Save last iteration's scores before first PV line is searched and all
         // the move scores but the (new) PV are set to -VALUE_INFINITE.
         for (size_t i = 0; i < RootMoves.size(); i++)
             RootMoves[i].prevScore = RootMoves[i].score;
 
-        prevBestMoveChanges = BestMoveChanges; // Only sensible when PVSize == 1
-        BestMoveChanges = 0;
-
         // MultiPV loop. We perform a full root search for each PV line
         for (PVIdx = 0; PVIdx < PVSize; PVIdx++)
         {
@@ -438,7 +438,7 @@ namespace {
 
             // Take in account some extra time if the best move has changed
             if (depth > 4 && depth < 50 &&  PVSize == 1)
-                TimeMgr.pv_instability(BestMoveChanges, prevBestMoveChanges);
+                TimeMgr.pv_instability(BestMoveChanges);
 
             // Stop search if most of available time is already consumed. We
             // probably don't have enough time to search the first move at the
@@ -664,7 +664,7 @@ namespace {
     // Step 8. Null move search with verification search (is omitted in PV nodes)
     if (   !PvNode
         && !ss->skipNullMove
-        &&  depth > ONE_PLY
+        &&  depth >= 2 * ONE_PLY
         &&  eval >= beta
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY
         &&  pos.non_pawn_material(pos.side_to_move()))
@@ -775,7 +775,10 @@ 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;
+    improving =   ss->staticEval >= (ss-2)->staticEval
+               || ss->staticEval == VALUE_NONE
+               ||(ss-2)->staticEval == VALUE_NONE;
+
     singularExtensionNode =   !RootNode
                            && !SpNode
                            &&  depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY)
@@ -1228,6 +1231,7 @@ moves_loop: // When in check and at SpNode search starts from here
           && !givesCheck
           &&  move != ttMove
           &&  type_of(move) != PROMOTION
+          &&  futilityBase > -VALUE_KNOWN_WIN
           && !pos.is_passed_pawn_push(move))
       {
           futilityValue =  futilityBase
@@ -1573,7 +1577,7 @@ 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_3], *st = state;
+  StateInfo state[MAX_PLY_PLUS_6], *st = state;
   const TTEntry* tte;
   int ply = 0;
   Move m = pv[0];
@@ -1606,7 +1610,7 @@ void RootMove::extract_pv_from_tt(Position& pos) {
 
 void RootMove::insert_pv_in_tt(Position& pos) {
 
-  StateInfo state[MAX_PLY_PLUS_3], *st = state;
+  StateInfo state[MAX_PLY_PLUS_6], *st = state;
   const TTEntry* tte;
   int ply = 0;
 
@@ -1681,7 +1685,7 @@ void Thread::idle_loop() {
 
           Threads.mutex.unlock();
 
-          Stack stack[MAX_PLY_PLUS_3], *ss = stack+2; // To allow referencing (ss-2)
+          Stack stack[MAX_PLY_PLUS_6], *ss = stack+2; // To allow referencing (ss-2)
           Position pos(*sp->pos, this);
 
           std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack));