Introduce Optimism

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 11d1df326bccf1a63238db6a2e3c01021a81b527..1dfadd21ab6b0009fc2817754036d130e7a1c00e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -334,8 +334,10 @@ void Thread::search() {
 
   nodesLastExplosive = nodes;
   nodesLastNormal    = nodes;
-  state = EXPLOSION_NONE;
-  trend = SCORE_ZERO;
+  state              = EXPLOSION_NONE;
+  trend              = SCORE_ZERO;
+  optimism[ us]      = Value(25);
+  optimism[~us]      = -optimism[us];
 
   int searchAgainCounter = 0;
 
@@ -381,11 +383,14 @@ void Thread::search() {
               alpha = std::max(prev - delta,-VALUE_INFINITE);
               beta  = std::min(prev + delta, VALUE_INFINITE);
 
-              // Adjust trend based on root move's previousScore (dynamic contempt)
-              int tr = 113 * prev / (abs(prev) + 147);
-
+              // Adjust trend and optimism based on root move's previousScore
+              int tr = sigmoid(prev, 0, 0, 147, 113, 1);
               trend = (us == WHITE ?  make_score(tr, tr / 2)
                                    : -make_score(tr, tr / 2));
+
+              int opt = sigmoid(prev, 0, 25, 147, 14464, 256);
+              optimism[ us] = Value(opt);
+              optimism[~us] = -optimism[us];
           }
 
           // Start with a small aspiration window and, in the case of a fail
@@ -1164,15 +1169,12 @@ moves_loop: // When in check, search starts here
       {
           Depth r = reduction(improving, depth, moveCount, rangeReduction > 2);
 
-          // Decrease reduction if on the PV (~2 Elo)
+          // Decrease reduction at some PvNodes (~2 Elo)
           if (   PvNode
-              && bestMoveCount <= 3)
+              && bestMoveCount <= 3
+              && beta - alpha >= thisThread->rootDelta / 4)
               r--;
 
-          // Increases reduction for PvNodes that have small window
-          if (PvNode && beta - alpha < thisThread->rootDelta / 4)
-              r++;
-
           // Decrease reduction if position is or has been on the PV
           // and node is not likely to fail low. (~3 Elo)
           if (   ss->ttPv
@@ -1756,10 +1758,6 @@ moves_loop: // When in check, search starts here
     thisThread->mainHistory[us][from_to(move)] << bonus;
     update_continuation_histories(ss, pos.moved_piece(move), to_sq(move), bonus);
 
-    // Penalty for reversed move in case of moved piece not being a pawn
-    if (type_of(pos.moved_piece(move)) != PAWN)
-        thisThread->mainHistory[us][from_to(reverse_move(move))] << -bonus;
-
     // Update countermove history
     if (is_ok((ss-1)->currentMove))
     {