Simplify Futility pruning for captures

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index f58def601382cb91aafca78f9ae3b89931a8591f..32eeedab4ae281d707ef5d4da067f2121c75302a 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -409,7 +409,7 @@ void Thread::search() {
               else
                   break;
 
-              delta += delta / 4 + 2;
+              delta += delta / 3;
 
               assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
           }
@@ -989,7 +989,7 @@ moves_loop: // When in check, search starts here
                   && lmrDepth < 7
                   && !ss->inCheck
                   && ss->staticEval + 207 + 223 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
-                   + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] * 1078 / 7000 < alpha)
+                   + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 7 < alpha)
                   continue;
 
               Bitboard occupied;
@@ -1037,7 +1037,7 @@ moves_loop: // When in check, search starts here
               lmrDepth = std::max(lmrDepth, 0);
 
               // Prune moves with negative SEE (~4 Elo)
-              if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth - 33 * lmrDepth / 2)))
+              if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth - 16 * lmrDepth)))
                   continue;
           }
       }
@@ -1317,10 +1317,11 @@ moves_loop: // When in check, search starts here
               else
               {
                   // Reduce other moves if we have found at least one score improvement (~1 Elo)
+                  // Reduce more for depth > 3 and depth < 12 (~1 Elo)
                   if (   depth > 1
                       && beta  <  14001
                       && value > -12754)
-                      depth -= 1;
+                      depth -= depth > 3 && depth < 12 ? 2 : 1;
 
                   assert(depth > 0);
                   alpha = value; // Update alpha! Always alpha < beta