Simplify capture pruning margin formula

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 7cc0542ab0cdbb8abeb821593fb2de45816d8209..3a80e161ff42238a3eb77c396e9a0feb80159fcc 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -71,16 +71,6 @@ namespace {
     return Value((175 - 50 * improving) * d / ONE_PLY);
   }
 
-  // Margin for pruning capturing moves: almost linear in depth
-  constexpr int CapturePruneMargin[] = { 0,
-                                         1 * PawnValueEg * 1055 / 1000,
-                                         2 * PawnValueEg * 1042 / 1000,
-                                         3 * PawnValueEg * 963  / 1000,
-                                         4 * PawnValueEg * 1038 / 1000,
-                                         5 * PawnValueEg * 950  / 1000,
-                                         6 * PawnValueEg * 930  / 1000
-                                       };
-
   // Futility and reductions lookup tables, initialized at startup
   int FutilityMoveCounts[2][16]; // [improving][depth]
   int Reductions[2][2][64][64];  // [pv][improving][depth][moveNumber]
@@ -296,6 +286,7 @@ void Thread::search() {
   MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
   double timeReduction = 1.0;
   Color us = rootPos.side_to_move();
+  bool failedLow;
 
   std::memset(ss-4, 0, 7 * sizeof(Stack));
   for (int i = 4; i > 0; i--)
@@ -305,7 +296,7 @@ void Thread::search() {
   beta = VALUE_INFINITE;
 
   if (mainThread)
-      mainThread->bestMoveChanges = 0, mainThread->failedLow = false;
+      mainThread->bestMoveChanges = 0, failedLow = false;
 
   size_t multiPV = Options["MultiPV"];
   Skill skill(Options["Skill Level"]);
@@ -346,7 +337,7 @@ void Thread::search() {
 
       // Age out PV variability metric
       if (mainThread)
-          mainThread->bestMoveChanges *= 0.517, mainThread->failedLow = false;
+          mainThread->bestMoveChanges *= 0.517, failedLow = false;
 
       // Save the last iteration's scores before first PV line is searched and
       // all the move scores except the (new) PV are set to -VALUE_INFINITE.
@@ -423,7 +414,7 @@ void Thread::search() {
 
                   if (mainThread)
                   {
-                      mainThread->failedLow = true;
+                      failedLow = true;
                       Threads.stopOnPonderhit = false;
                   }
               }
@@ -471,7 +462,7 @@ void Thread::search() {
           && !Threads.stop
           && !Threads.stopOnPonderhit)
           {
-              const int F[] = { mainThread->failedLow,
+              const int F[] = { failedLow,
                                 bestValue - mainThread->previousScore };
 
               int improvingFactor = std::max(246, std::min(832, 306 + 119 * F[0] - 6 * F[1]));
@@ -522,7 +513,7 @@ namespace {
     constexpr bool PvNode = NT == PV;
     const bool rootNode = PvNode && ss->ply == 0;
 
-    // Check if we have an upcoming move which draws by repetition, or 
+    // 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
@@ -962,7 +953,7 @@ moves_loop: // When in check, search starts from here
           }
           else if (    depth < 7 * ONE_PLY // (~20 Elo)
                    && !extension
-                   && !pos.see_ge(move, -Value(CapturePruneMargin[depth / ONE_PLY])))
+                   && !pos.see_ge(move, -Value(PawnValueEg * (depth / ONE_PLY))))
                   continue;
       }
 
@@ -1164,8 +1155,8 @@ moves_loop: // When in check, search starts from here
     {
         // Quiet best move: update move sorting heuristics
         if (!pos.capture_or_promotion(bestMove))
-            update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount, 
-                                                          stat_bonus(depth + (bestValue > beta + PawnValueMg ? ONE_PLY : DEPTH_ZERO)));
+            update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount,
+                               stat_bonus(depth + (bestValue > beta + PawnValueMg ? ONE_PLY : DEPTH_ZERO)));
         else
             update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY));