Change depth - 1 to newDepth

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 5c53c0dae8bf6a14dade4b2ee3fe5b55f21eff0b..7d567b8ab71058d9b6c78b2424142da9f568ec16 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -372,8 +372,8 @@ void Thread::search() {
             beta      = std::min(avg + delta, VALUE_INFINITE);
 
             // Adjust optimism based on root move's averageScore (~4 Elo)
-            optimism[us]  = 103 * avg / (std::abs(avg) + 119);
-            optimism[~us] = -116 * avg / (std::abs(avg) + 123);
+            optimism[us]  = 110 * avg / (std::abs(avg) + 121);
+            optimism[~us] = -optimism[us];
 
             // Start with a small aspiration window and, in the case of a fail
             // high/low, re-search with a bigger window until we don't fail
@@ -1045,7 +1045,7 @@ moves_loop:  // When in check, search starts here
                 && tte->depth() >= depth - 3)
             {
                 Value singularBeta  = ttValue - (64 + 57 * (ss->ttPv && !PvNode)) * depth / 64;
-                Depth singularDepth = (depth - 1) / 2;
+                Depth singularDepth = newDepth / 2;
 
                 ss->excludedMove = move;
                 value =
@@ -1178,7 +1178,9 @@ moves_loop:  // When in check, search starts here
             // In general we want to cap the LMR depth search at newDepth, but when
             // reduction is negative, we allow this move a limited search extension
             // beyond the first move depth. This may lead to hidden double extensions.
-            Depth d = std::clamp(newDepth - r, 1, newDepth + 1);
+            // To prevent problems when the max value is less than the min value,
+            // std::clamp has been replaced by a more robust implementation.
+            Depth d = std::max(1, std::min(newDepth - r, newDepth + 1));
 
             value = -search<NonPV>(pos, ss + 1, -(alpha + 1), -alpha, d, true);