Do shallower search in case of lmr being not successful enough

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 422d4b43a8268b702dd02943bb434c78e0d99262..5839763dc7fd647fa8e91d92cb874e54368c1126 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -309,7 +309,6 @@ void Thread::search() {
 
   complexityAverage.set(155, 1);
 
-  trend = SCORE_ZERO;
   optimism[us] = optimism[~us] = VALUE_ZERO;
 
   int searchAgainCounter = 0;
@@ -356,11 +355,7 @@ void Thread::search() {
               alpha = std::max(prev - delta,-VALUE_INFINITE);
               beta  = std::min(prev + delta, VALUE_INFINITE);
 
-              // Adjust trend and optimism based on root move's previousScore
-              int tr = 116 * prev / (std::abs(prev) + 89);
-              trend = (us == WHITE ?  make_score(tr, tr / 2)
-                                   : -make_score(tr, tr / 2));
-
+              // Adjust optimism based on root move's previousScore
               int opt = 118 * prev / (std::abs(prev) + 169);
               optimism[ us] = Value(opt);
               optimism[~us] = -optimism[us];
@@ -1189,8 +1184,11 @@ moves_loop: // When in check, search starts here
           // Do full depth search when reduced LMR search fails high
           if (value > alpha && d < newDepth)
           {
+              // Adjust full depth search based on LMR results - if result
+              // was good enough search deeper, if it was bad enough search shallower
               const bool doDeeperSearch = value > (alpha + 64 + 11 * (newDepth - d));
-              value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth + doDeeperSearch, !cutNode);
+              const bool doShallowerSearch = value < bestValue + newDepth;
+              value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth + doDeeperSearch - doShallowerSearch, !cutNode);
 
               int bonus = value > alpha ?  stat_bonus(newDepth)
                                         : -stat_bonus(newDepth);