Qsearch simplification. (#1828)

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index d0bbc9675c9618ff780cb51b3f89a8eb8abf31f6..38d5683493a5b14df76a7196a340b49a8b429ebd 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -2,7 +2,7 @@
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
-  Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -85,10 +85,10 @@ namespace {
     return d > 17 ? 0 : 29 * d * d + 138 * d - 134;
   }
 
-  // Add a small random component to draw evaluations to keep search dynamic 
+  // Add a small random component to draw evaluations to keep search dynamic
   // and to avoid 3fold-blindness.
   Value value_draw(Depth depth, Thread* thisThread) {
-    return depth < 4 ? VALUE_DRAW 
+    return depth < 4 ? VALUE_DRAW
                      : VALUE_DRAW + Value(2 * (thisThread->nodes.load(std::memory_order_relaxed) % 2) - 1);
   }
 
@@ -187,6 +187,7 @@ void Search::clear() {
   Time.availableNodes = 0;
   TT.clear();
   Threads.clear();
+  Tablebases::init(Options["SyzygyPath"]); // Free up mapped files
 }
 
 
@@ -598,7 +599,7 @@ namespace {
         if (   Threads.stop.load(std::memory_order_relaxed)
             || pos.is_draw(ss->ply)
             || ss->ply >= MAX_PLY)
-            return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos) 
+            return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos)
                                                     : value_draw(depth, pos.this_thread());
 
         // Step 3. Mate distance pruning. Even if we mate at the next move our score
@@ -682,6 +683,10 @@ namespace {
             TB::ProbeState err;
             TB::WDLScore wdl = Tablebases::probe_wdl(pos, &err);
 
+            // Force check of time on the next occasion
+            if (thisThread == Threads.main())
+                static_cast<MainThread*>(thisThread)->callsCnt = 0;
+
             if (err != TB::ProbeState::FAIL)
             {
                 thisThread->tbHits.fetch_add(1, std::memory_order_relaxed);
@@ -943,10 +948,8 @@ moves_loop: // When in check, search starts from here
                &&  pos.see_ge(move))
           extension = ONE_PLY;
 
-      // Extension for king moves that change castling rights
-      if (   pos.can_castle(us)
-          && type_of(movedPiece) == KING
-          && depth < 12 * ONE_PLY)
+      else if (   pos.can_castle(us) // Extension for king moves that change castling rights
+               && type_of(movedPiece) == KING)
           extension = ONE_PLY;
 
       // Calculate new depth for this move
@@ -1392,21 +1395,15 @@ moves_loop: // When in check, search starts from here
 
           if (value > alpha)
           {
+              bestMove = move;
+
               if (PvNode) // Update pv even in fail-high case
                   update_pv(ss->pv, move, (ss+1)->pv);
 
               if (PvNode && value < beta) // Update alpha here!
-              {
                   alpha = value;
-                  bestMove = move;
-              }
-              else // Fail high
-              {
-                  tte->save(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
-                            ttDepth, move, ss->staticEval);
-
-                  return value;
-              }
+              else
+                  break; // Fail high
           }
        }
     }
@@ -1417,7 +1414,8 @@ moves_loop: // When in check, search starts from here
         return mated_in(ss->ply); // Plies to mate from the root
 
     tte->save(posKey, value_to_tt(bestValue, ss->ply),
-              PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
+              bestValue >= beta ? BOUND_LOWER :
+              PvNode && bestValue > oldAlpha  ? BOUND_EXACT : BOUND_UPPER,
               ttDepth, bestMove, ss->staticEval);
 
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);