Micro-optimize perft

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index b39750d17f8b874d128d88161bb8e9a2e3c14be5..f4f411c56d18f266f110d69ba5d4aa0b8c9707ad 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -91,7 +91,7 @@ namespace {
   CountermovesStats Countermoves;
 
   template <NodeType NT>
-  Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
+  Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
 
   template <NodeType NT, bool InCheck>
   Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
@@ -155,21 +155,17 @@ void Search::init() {
 
 size_t Search::perft(Position& pos, Depth depth) {
 
-  // At the last ply just return the number of legal moves (leaf nodes)
-  if (depth == ONE_PLY)
-      return MoveList<LEGAL>(pos).size();
-
   StateInfo st;
   size_t cnt = 0;
   CheckInfo ci(pos);
+  const bool leaf = depth == 2 * ONE_PLY;
 
   for (MoveList<LEGAL> it(pos); *it; ++it)
   {
       pos.do_move(*it, st, ci, pos.move_gives_check(*it, ci));
-      cnt += perft(pos, depth - ONE_PLY);
+      cnt += leaf ? MoveList<LEGAL>(pos).size() : perft(pos, depth - ONE_PLY);
       pos.undo_move(*it);
   }
-
   return cnt;
 }
 
@@ -349,7 +345,7 @@ namespace {
             // research with bigger window until not failing high/low anymore.
             while (true)
             {
-                bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY);
+                bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY, false);
 
                 // Bring to front the best move. It is critical that sorting is
                 // done with a stable algorithm because all the values but the first
@@ -419,7 +415,7 @@ namespace {
                 rm = *std::find(RootMoves.begin(), RootMoves.end(), skill.best);
 
             Log log(Options["Search Log Filename"]);
-            log << pretty_pv(pos, depth, rm.score, Time::now() - SearchTime, rm.pv.data())
+            log << pretty_pv(pos, depth, rm.score, Time::now() - SearchTime, &rm.pv[0])
                 << std::endl;
         }
 
@@ -455,7 +451,7 @@ namespace {
                 Value rBeta = bestValue - 2 * PawnValueMg;
                 ss->excludedMove = RootMoves[0].pv[0];
                 ss->skipNullMove = true;
-                Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY);
+                Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY, true);
                 ss->skipNullMove = false;
                 ss->excludedMove = MOVE_NONE;
 
@@ -485,7 +481,7 @@ namespace {
   // here: This is taken care of after we return from the split point.
 
   template <NodeType NT>
-  Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
+  Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
 
     const bool PvNode   = (NT == PV || NT == Root || NT == SplitPointPV || NT == SplitPointRoot);
     const bool SpNode   = (NT == SplitPointPV || NT == SplitPointNonPV || NT == SplitPointRoot);
@@ -679,7 +675,7 @@ namespace {
         pos.do_null_move(st);
         (ss+1)->skipNullMove = true;
         nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
-                                      : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R);
+                                      : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R, !cutNode);
         (ss+1)->skipNullMove = false;
         pos.undo_null_move();
 
@@ -694,7 +690,7 @@ namespace {
 
             // Do verification search at high depths
             ss->skipNullMove = true;
-            Value v = search<NonPV>(pos, ss, alpha, beta, depth-R);
+            Value v = search<NonPV>(pos, ss, alpha, beta, depth-R, false);
             ss->skipNullMove = false;
 
             if (v >= beta)
@@ -726,7 +722,6 @@ namespace {
         &&  depth >= 5 * ONE_PLY
         && !inCheck
         && !ss->skipNullMove
-        &&  excludedMove == MOVE_NONE
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY)
     {
         Value rbeta = beta + 200;
@@ -744,7 +739,7 @@ namespace {
             {
                 ss->currentMove = move;
                 pos.do_move(move, st, ci, pos.move_gives_check(move, ci));
-                value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth);
+                value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
                 pos.undo_move(move);
                 if (value >= rbeta)
                     return value;
@@ -759,7 +754,7 @@ namespace {
         Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
 
         ss->skipNullMove = true;
-        search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d);
+        search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d, true);
         ss->skipNullMove = false;
 
         tte = TT.probe(posKey);
@@ -855,7 +850,7 @@ split_point_start: // At split points actual search starts from here
           Value rBeta = ttValue - int(depth);
           ss->excludedMove = move;
           ss->skipNullMove = true;
-          value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2);
+          value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
           ss->skipNullMove = false;
           ss->excludedMove = MOVE_NONE;
 
@@ -948,6 +943,10 @@ split_point_start: // At split points actual search starts from here
           &&  move != ss->killers[1])
       {
           ss->reduction = reduction<PvNode>(depth, moveCount);
+
+          if (!PvNode && cutNode)
+              ss->reduction += ONE_PLY;
+
           if (move == countermoves[0] || move == countermoves[1])
               ss->reduction = std::max(DEPTH_ZERO, ss->reduction-ONE_PLY);
 
@@ -955,7 +954,7 @@ split_point_start: // At split points actual search starts from here
           if (SpNode)
               alpha = splitPoint->alpha;
 
-          value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
+          value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
 
           doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
           ss->reduction = DEPTH_ZERO;
@@ -972,7 +971,7 @@ split_point_start: // At split points actual search starts from here
           value = newDepth < ONE_PLY ?
                           givesCheck ? -qsearch<NonPV,  true>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
                                      : -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
-                                     : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
+                                     : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
       }
 
       // Only for PV nodes do a full PV search on the first move or after a fail
@@ -982,7 +981,7 @@ split_point_start: // At split points actual search starts from here
           value = newDepth < ONE_PLY ?
                           givesCheck ? -qsearch<PV,  true>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
                                      : -qsearch<PV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
-                                     : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
+                                     : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false);
       // Step 17. Undo move
       pos.undo_move(move);
 
@@ -1057,7 +1056,7 @@ split_point_start: // At split points actual search starts from here
           assert(bestValue < beta);
 
           thisThread->split<FakeSplit>(pos, ss, alpha, beta, &bestValue, &bestMove,
-                                       depth, threatMove, moveCount, &mp, NT);
+                                       depth, threatMove, moveCount, &mp, NT, cutNode);
           if (bestValue >= beta)
               break;
       }
@@ -1705,13 +1704,13 @@ void Thread::idle_loop() {
 
           switch (sp->nodeType) {
           case Root:
-              search<SplitPointRoot>(pos, ss, sp->alpha, sp->beta, sp->depth);
+              search<SplitPointRoot>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
               break;
           case PV:
-              search<SplitPointPV>(pos, ss, sp->alpha, sp->beta, sp->depth);
+              search<SplitPointPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
               break;
           case NonPV:
-              search<SplitPointNonPV>(pos, ss, sp->alpha, sp->beta, sp->depth);
+              search<SplitPointNonPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
               break;
           default:
               assert(false);