Using a S-curve for the optimism measure

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index f6cf8de887cc655512884249d70301196b0e5a70..f7c13bbf24ecb816b87a2f4d540a9e695dc91393 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -346,11 +346,13 @@ void Thread::search() {
               alpha = std::max(rootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
               beta  = std::min(rootMoves[PVIdx].previousScore + delta, VALUE_INFINITE);
 
-              // Adjust contempt based on current bestValue
-              ct =  Options["Contempt"] * PawnValueEg / 100 // From centipawns
-                  + (bestValue >  500 ?  50:                // Dynamic contempt
-                     bestValue < -500 ? -50:
-                     bestValue / 10);
+              ct =  Options["Contempt"] * PawnValueEg / 100; // From centipawns
+
+              // Adjust contempt based on current bestValue (dynamic contempt)
+              int sign = (bestValue > 0) - (bestValue < 0);
+              ct +=  bestValue >  500 ?  70 :
+                     bestValue < -500 ? -70 :
+                     bestValue / 10 + sign * int(std::round(3.22 * log(1 + abs(bestValue))));
 
               Eval::Contempt = (us == WHITE ?  make_score(ct, ct / 2)
                                             : -make_score(ct, ct / 2));
@@ -757,10 +759,13 @@ namespace {
 
         Value rbeta = std::min(beta + 200, VALUE_INFINITE);
         MovePicker mp(pos, ttMove, rbeta - ss->staticEval, &thisThread->captureHistory);
-
-        while ((move = mp.next_move()) != MOVE_NONE)
+        int probCutCount = 0;
+        while (  (move = mp.next_move()) != MOVE_NONE
+               && probCutCount < depth / ONE_PLY - 3)
             if (pos.legal(move))
             {
+                probCutCount++;
+
                 ss->currentMove = move;
                 ss->contHistory = thisThread->contHistory[pos.moved_piece(move)][to_sq(move)].get();