Simplify locking in sp_search and sp_search_pv

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 2fece7cee10cf9e3891db8afe3641d845e09ed78..c3c2925fcf70f5dfff640875fd1295be5d924606 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1411,9 +1411,14 @@ namespace {
         update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
     }
 
-    // Post futility pruning
-    if (depth < SelectiveDepth && staticValue - PostFutilityValueMargin >= beta)
-        return (staticValue - PostFutilityValueMargin);
+    // Do a "stand pat". If we are above beta by a good margin then
+    // return immediately.
+    // FIXME: test with added condition 'allowNullmove || depth <= OnePly' and !value_is_mate(beta)
+    // FIXME: test with modified condition 'depth < RazorDepth'
+    if (  !isCheck
+        && depth < SelectiveDepth
+        && staticValue - PostFutilityValueMargin >= beta)
+        return staticValue - PostFutilityValueMargin;
 
     // Null move search
     if (    allowNullmove
@@ -1537,29 +1542,6 @@ namespace {
       // Update current move
       movesSearched[moveCount++] = ss[ply].currentMove = move;
 
-      // Futility pruning for captures
-      Color them = opposite_color(pos.side_to_move());
-
-      if (   !isCheck
-          && newDepth < SelectiveDepth
-          && !dangerous
-          && pos.move_is_capture(move)
-          && !pos.move_is_check(move, ci)
-          && !move_is_promotion(move)
-          && move != ttMove
-          && !move_is_ep(move)
-          && (pos.type_of_piece_on(move_to(move)) != PAWN || !pos.pawn_is_passed(them, move_to(move)))) // Do not prune passed pawn captures
-      {
-          int preFutilityValueMargin = 0;
-
-          if (newDepth >= OnePly)
-              preFutilityValueMargin = 112 * bitScanReverse32(int(newDepth) * int(newDepth) / 2);
-
-          if (ss[ply].eval + pos.endgame_value_of_piece_on(move_to(move)) + preFutilityValueMargin + ei.futilityMargin + 90 < beta)
-              continue;
-      }
-
-
       // Futility pruning
       if (   !isCheck
           && !dangerous
@@ -1892,28 +1874,29 @@ namespace {
     SearchStack* ss = sp->sstack[threadID];
     Value value = -VALUE_INFINITE;
     Move move;
+    int moveCount;
     bool isCheck = pos.is_check();
     bool useFutilityPruning =     sp->depth < SelectiveDepth
                               && !isCheck;
 
     const int FutilityMoveCountMargin = 3 + (1 << (3 * int(sp->depth) / 8));
 
-    while (    sp->bestValue < sp->beta
+    while (    lock_grab_bool(&(sp->lock))
+           &&  sp->bestValue < sp->beta
            && !thread_should_stop(threadID)
-           && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
+           && (move = sp->mp->get_next_move()) != MOVE_NONE)
     {
+      moveCount = ++sp->moves;
+      lock_release(&(sp->lock));
+
       assert(move_is_ok(move));
 
       bool moveIsCheck = pos.move_is_check(move, ci);
       bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
 
-      lock_grab(&(sp->lock));
-      int moveCount = ++sp->moves;
-      lock_release(&(sp->lock));
-
       ss[sp->ply].currentMove = move;
 
-      // Decide the new search depth.
+      // Decide the new search depth
       bool dangerous;
       Depth ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, false, &dangerous);
       Depth newDepth = sp->depth - OnePly + ext;
@@ -2000,7 +1983,7 @@ namespace {
       }
     }
 
-    lock_grab(&(sp->lock));
+    /* Here we have the lock still grabbed */
 
     // If this is the master thread and we have been asked to stop because of
     // a beta cutoff higher up in the tree, stop all slave threads.
@@ -2033,24 +2016,25 @@ namespace {
     CheckInfo ci(pos);
     SearchStack* ss = sp->sstack[threadID];
     Value value = -VALUE_INFINITE;
+    int moveCount;
     Move move;
 
-    while (    sp->alpha < sp->beta
+    while (    lock_grab_bool(&(sp->lock))
+           &&  sp->alpha < sp->beta
            && !thread_should_stop(threadID)
-           && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
+           && (move = sp->mp->get_next_move()) != MOVE_NONE)
     {
-      bool moveIsCheck = pos.move_is_check(move, ci);
-      bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
+      moveCount = ++sp->moves;
+      lock_release(&(sp->lock));
 
       assert(move_is_ok(move));
 
-      lock_grab(&(sp->lock));
-      int moveCount = ++sp->moves;
-      lock_release(&(sp->lock));
+      bool moveIsCheck = pos.move_is_check(move, ci);
+      bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
 
       ss[sp->ply].currentMove = move;
 
-      // Decide the new search depth.
+      // Decide the new search depth
       bool dangerous;
       Depth ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
       Depth newDepth = sp->depth - OnePly + ext;
@@ -2149,7 +2133,7 @@ namespace {
       }
     }
 
-    lock_grab(&(sp->lock));
+    /* Here we have the lock still grabbed */
 
     // If this is the master thread and we have been asked to stop because of
     // a beta cutoff higher up in the tree, stop all slave threads.