Simplify capture bonus

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 0574da5897274c2653f82234675a08545de9c644..5e3e61b2011925bd3fad886481325098e3ecf634 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -519,13 +519,25 @@ namespace {
   template <NodeType NT>
   Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
 
-    // Use quiescence search when needed
-    if (depth < ONE_PLY)
-        return qsearch<NT>(pos, ss, alpha, beta);
-
     constexpr bool PvNode = NT == PV;
     const bool rootNode = PvNode && ss->ply == 0;
 
+    // Check if we have an upcoming move which draws by repetition, or 
+    // if the opponent had an alternative move earlier to this position.
+    if (   pos.rule50_count() >= 3
+        && alpha < VALUE_DRAW
+        && !rootNode
+        && pos.has_game_cycle(ss->ply))
+    {
+        alpha = VALUE_DRAW;
+        if (alpha >= beta)
+            return alpha;
+    }
+
+    // Dive into quiescence search when the depth reaches zero
+    if (depth < ONE_PLY)
+        return qsearch<NT>(pos, ss, alpha, beta);
+
     assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
     assert(PvNode || (alpha == beta - 1));
     assert(DEPTH_ZERO < depth && depth < DEPTH_MAX);
@@ -578,17 +590,6 @@ namespace {
         beta = std::min(mate_in(ss->ply+1), beta);
         if (alpha >= beta)
             return alpha;
-
-        // Check if there exists a move which draws by repetition, or an alternative
-        // earlier move to this position.
-        if (   pos.rule50_count() >= 3
-            && alpha < VALUE_DRAW
-            && pos.has_game_cycle(ss->ply))
-        {
-            alpha = VALUE_DRAW;
-            if (alpha >= beta)
-                return alpha;
-        }
     }
 
     assert(0 <= ss->ply && ss->ply < MAX_PLY);
@@ -751,7 +752,7 @@ namespace {
         &&  ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
         && !excludedMove
         &&  pos.non_pawn_material(us)
-        && (ss->ply > thisThread->nmpMinPly || us != thisThread->nmpColor))
+        && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
     {
         assert(eval - beta >= 0);
 
@@ -780,7 +781,7 @@ namespace {
 
             // Do verification search at high depths, with null move pruning disabled
             // for us, until ply exceeds nmpMinPly.
-            thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4 - 1;
+            thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4;
             thisThread->nmpColor = us;
 
             Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
@@ -1165,8 +1166,7 @@ moves_loop: // When in check, search starts from here
         if (!pos.capture_or_promotion(bestMove))
             update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth));
         else
-            update_capture_stats(pos, bestMove, capturesSearched, captureCount,
-                                 stat_bonus(depth + (bestValue > beta + KnightValueMg ? ONE_PLY : DEPTH_ZERO)));
+            update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY));
 
         // Extra penalty for a quiet TT move in previous ply when it gets refuted
         if ((ss-1)->moveCount == 1 && !pos.captured_piece())