Clean-up skipEarlyPruning (#921)

make skipEarlyPruning a search argument instead of managing this by hand.

Verified for no regression at STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 96754 W: 17089 L: 17095 D: 62570

No functional change.

diff --git a/src/search.cpp b/src/search.cpp
index 2fa2ce7e27cb4e41c0243a8f55f987b3d8f2dd35..57f636535ba89ac192a87196494f748457da3993 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -162,7 +162,7 @@ namespace {
   Value DrawValue[COLOR_NB];
 
   template <NodeType NT>
-  Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
+  Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning);
 
   template <NodeType NT, bool InCheck>
   Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
@@ -407,7 +407,7 @@ void Thread::search() {
           // high/low anymore.
           while (true)
           {
-              bestValue = ::search<PV>(rootPos, ss, alpha, beta, rootDepth, false);
+              bestValue = ::search<PV>(rootPos, ss, alpha, beta, rootDepth, false, false);
 
               // Bring the best move to the front. It is critical that sorting
               // is done with a stable algorithm because all the values but the
@@ -541,7 +541,7 @@ namespace {
   // search<>() is the main search function for both PV and non-PV nodes
 
   template <NodeType NT>
-  Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
+  Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning) {
 
     const bool PvNode = NT == PV;
     const bool rootNode = PvNode && (ss-1)->ply == 0;
@@ -617,7 +617,6 @@ namespace {
 
     ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
     ss->counterMoves = nullptr;
-    (ss+1)->skipEarlyPruning = false;
     (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
     Square prevSq = to_sq((ss-1)->currentMove);
 
@@ -712,7 +711,7 @@ namespace {
                   ss->staticEval, TT.generation());
     }
 
-    if (ss->skipEarlyPruning)
+    if (skipEarlyPruning)
         goto moves_loop;
 
     // Step 6. Razoring (skipped when in check)
@@ -753,10 +752,8 @@ namespace {
         Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
 
         pos.do_null_move(st);
-        (ss+1)->skipEarlyPruning = true;
         nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1, DEPTH_ZERO)
-                                      : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
-        (ss+1)->skipEarlyPruning = false;
+                                      : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true);
         pos.undo_null_move();
 
         if (nullValue >= beta)
@@ -769,10 +766,8 @@ namespace {
                 return nullValue;
 
             // Do verification search at high depths
-            ss->skipEarlyPruning = true;
             Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta, DEPTH_ZERO)
-                                        :  search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
-            ss->skipEarlyPruning = false;
+                                        :  search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
 
             if (v >= beta)
                 return nullValue;
@@ -801,7 +796,7 @@ namespace {
                 ss->currentMove = move;
                 ss->counterMoves = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)];
                 pos.do_move(move, st);
-                value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
+                value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode, false);
                 pos.undo_move(move);
                 if (value >= rbeta)
                     return value;
@@ -814,9 +809,7 @@ namespace {
         && (PvNode || ss->staticEval + 256 >= beta))
     {
         Depth d = (3 * depth / (4 * ONE_PLY) - 2) * ONE_PLY;
-        ss->skipEarlyPruning = true;
-        search<NT>(pos, ss, alpha, beta, d, cutNode);
-        ss->skipEarlyPruning = false;
+        search<NT>(pos, ss, alpha, beta, d, cutNode, true);
 
         tte = TT.probe(posKey, ttHit);
         ttMove = ttHit ? tte->move() : MOVE_NONE;
@@ -898,9 +891,7 @@ moves_loop: // When in check search starts from here
           Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
           Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY;
           ss->excludedMove = move;
-          ss->skipEarlyPruning = true;
-          value = search<NonPV>(pos, ss, rBeta - 1, rBeta, d, cutNode);
-          ss->skipEarlyPruning = false;
+          value = search<NonPV>(pos, ss, rBeta - 1, rBeta, d, cutNode, true);
           ss->excludedMove = MOVE_NONE;
 
           if (value < rBeta)
@@ -1014,7 +1005,7 @@ moves_loop: // When in check search starts from here
 
           Depth d = std::max(newDepth - r, ONE_PLY);
 
-          value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
+          value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true, false);
 
           doFullDepthSearch = (value > alpha && d != newDepth);
       }
@@ -1026,7 +1017,7 @@ moves_loop: // When in check 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, !cutNode);
+                                       : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false);
 
       // For PV nodes only, do a full PV search on the first move or after a fail
       // high (in the latter case search only if value < beta), otherwise let the
@@ -1039,7 +1030,7 @@ moves_loop: // When in check 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, false);
+                                       : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, false);
       }
 
       // Step 17. Undo move

diff --git a/src/search.h b/src/search.h
index d8051ec0321fc354ff1d8b0a60eda15a2f69fc8a..c2d5d8e9295d424ae130a411436cbb99b1ff0581 100644 (file)
--- a/src/search.h
+++ b/src/search.h
@@ -38,15 +38,14 @@ namespace Search {
 
 struct Stack {
   Move* pv;
+  CounterMoveStats* counterMoves;
   int ply;
   Move currentMove;
   Move excludedMove;
   Move killers[2];
   Value staticEval;
   Value history;
-  bool skipEarlyPruning;
   int moveCount;
-  CounterMoveStats* counterMoves;
 };