Simplify trend and optimism.

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 1257637895fe4c93e13375a8b883e2febd972914..0f524093c2d399c40ae08c25889f19aabf49b302 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -309,9 +309,8 @@ void Thread::search() {
 
   complexityAverage.set(155, 1);
 
-  trend         = SCORE_ZERO;
-  optimism[ us] = Value(37);
-  optimism[~us] = -optimism[us];
+  trend = SCORE_ZERO;
+  optimism[us] = optimism[~us] = VALUE_ZERO;
 
   int searchAgainCounter = 0;
 
@@ -358,11 +357,11 @@ void Thread::search() {
               beta  = std::min(prev + delta, VALUE_INFINITE);
 
               // Adjust trend and optimism based on root move's previousScore
-              int tr = sigmoid(prev, 3, 10, 89, 116, 1);
+              int tr = 116 * prev / (std::abs(prev) + 89);
               trend = (us == WHITE ?  make_score(tr, tr / 2)
                                    : -make_score(tr, tr / 2));
 
-              int opt = sigmoid(prev, 7, 20, 169, 19350, 164);
+              int opt = 118 * prev / (std::abs(prev) + 169);
               optimism[ us] = Value(opt);
               optimism[~us] = -optimism[us];
           }
@@ -1059,7 +1058,7 @@ moves_loop: // When in check, search starts here
               && (tte->bound() & BOUND_LOWER)
               &&  tte->depth() >= depth - 3)
           {
-              Value singularBeta = ttValue - 3 * depth;
+              Value singularBeta = ttValue - (3 + (ss->ttPv && !PvNode)) * depth;
               Depth singularDepth = (depth - 1) / 2;
 
               ss->excludedMove = move;