X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=7dc674882ee4315b3fe8922c7ab6d2252ab456c9;hp=507339504600cb2e49bc1cbe5c6558e59784fd86;hb=97d2cc9a9c1c4b6ff1b470676fa18c7fc6509886;hpb=3ac3b68540e93770e5a806196537c0e9a2d81a67

diff --git a/src/search.cpp b/src/search.cpp
index 50733950..7dc67488 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -85,6 +85,13 @@ namespace {
     return d > 17 ? 0 : 29 * d * d + 138 * d - 134;
   }
 
+  // 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 
+                     : VALUE_DRAW + Value(2 * (thisThread->nodes.load(std::memory_order_relaxed) % 2) - 1);
+  }
+
   // Skill structure is used to implement strength limit
   struct Skill {
     explicit Skill(int l) : level(l) {}
@@ -535,7 +542,7 @@ namespace {
         && !rootNode
         && pos.has_game_cycle(ss->ply))
     {
-        alpha = VALUE_DRAW;
+        alpha = value_draw(depth, pos.this_thread());
         if (alpha >= beta)
             return alpha;
     }
@@ -584,8 +591,8 @@ 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) - 10 * ((ss-1)->statScore > 0)
-                                                    : VALUE_DRAW;
+            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
         // would be at best mate_in(ss->ply+1), but if alpha is already bigger because
@@ -705,15 +712,16 @@ namespace {
     // Step 6. Static evaluation of the position
     if (inCheck)
     {
-        ss->staticEval = pureStaticEval = eval = VALUE_NONE;
+        ss->staticEval = eval = pureStaticEval = VALUE_NONE;
         improving = false;
         goto moves_loop;  // Skip early pruning when in check
     }
     else if (ttHit)
     {
         // Never assume anything on values stored in TT
-        if ((ss->staticEval = pureStaticEval = eval = tte->eval()) == VALUE_NONE)
-            eval = ss->staticEval = pureStaticEval = evaluate(pos);
+        ss->staticEval = eval = pureStaticEval = tte->eval();
+        if (eval == VALUE_NONE)
+            ss->staticEval = eval = pureStaticEval = evaluate(pos);
 
         // Can ttValue be used as a better position evaluation?
         if (    ttValue != VALUE_NONE
@@ -722,12 +730,17 @@ namespace {
     }
     else
     {
-        int p = (ss-1)->statScore;
-        int malus = p > 0 ? (p + 5000) / 1024 :
-                    p < 0 ? (p - 5000) / 1024 : 0;
+        if ((ss-1)->currentMove != MOVE_NULL)
+        {
+            int p = (ss-1)->statScore;
+            int bonus = p > 0 ? (-p - 2500) / 512 :
+                        p < 0 ? (-p + 2500) / 512 : 0;
 
-        ss->staticEval = eval = (ss-1)->currentMove != MOVE_NULL ? (pureStaticEval = evaluate(pos)) - malus
-                                                                 : (pureStaticEval = -(ss-1)->staticEval + 2 * Eval::Tempo);
+            pureStaticEval = evaluate(pos);
+            ss->staticEval = eval = pureStaticEval + bonus;
+        }
+        else
+            ss->staticEval = eval = pureStaticEval = -(ss-1)->staticEval + 2 * Eval::Tempo;
 
         tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, pureStaticEval);
     }
@@ -752,7 +765,7 @@ namespace {
         && (ss-1)->currentMove != MOVE_NULL
         && (ss-1)->statScore < 23200
         &&  eval >= beta
-        &&  ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
+        &&  pureStaticEval >= beta - 36 * depth / ONE_PLY + 225
         && !excludedMove
         &&  pos.non_pawn_material(us)
         && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
@@ -760,7 +773,7 @@ namespace {
         assert(eval - beta >= 0);
 
         // Null move dynamic reduction based on depth and value
-        Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
+        Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min(int(eval - beta) / 200, 3)) * ONE_PLY;
 
         ss->currentMove = MOVE_NULL;
         ss->continuationHistory = &thisThread->continuationHistory[NO_PIECE][0];
@@ -809,7 +822,7 @@ namespace {
 
         while (  (move = mp.next_move()) != MOVE_NONE
                && probCutCount < 3)
-            if (pos.legal(move))
+            if (move != excludedMove && pos.legal(move))
             {
                 probCutCount++;
 
@@ -858,7 +871,7 @@ moves_loop: // When in check, search starts from here
     value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
 
     skipQuiets = false;
-    ttCapture = false;
+    ttCapture = ttMove && pos.capture_or_promotion(ttMove);
     pvExact = PvNode && ttHit && tte->bound() == BOUND_EXACT;
 
     // Step 12. Loop through all pseudo-legal moves until no moves remain
@@ -900,7 +913,7 @@ moves_loop: // When in check, search starts from here
       // Singular extension search (~60 Elo). If all moves but one fail low on a
       // search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
       // then that move is singular and should be extended. To verify this we do
-      // a reduced search on on all the other moves but the ttMove and if the
+      // a reduced search on all the other moves but the ttMove and if the
       // result is lower than ttValue minus a margin then we will extend the ttMove.
       if (    depth >= 8 * ONE_PLY
           &&  move == ttMove
@@ -977,9 +990,6 @@ moves_loop: // When in check, search starts from here
           continue;
       }
 
-      if (move == ttMove && captureOrPromotion)
-          ttCapture = true;
-
       // Update the current move (this must be done after singular extension search)
       ss->currentMove = move;
       ss->continuationHistory = &thisThread->continuationHistory[movedPiece][to_sq(move)];
@@ -1123,6 +1133,8 @@ moves_loop: // When in check, search starts from here
                   break;
               }
           }
+          else if (PvNode && !rootNode && value == alpha)
+              update_pv(ss->pv, move, (ss+1)->pv);
       }
 
       if (move != bestMove)