X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=c44d150f7008826abd9fe08ac4c1b0c4798e4985;hp=c894403cc452337c87abfc2d3cd99227b892a645;hb=3c7eebb48d5239cf363c54e082686f5559174518;hpb=c83fd08fd4fa91702ef0f727bc777c613524403d

diff --git a/src/search.cpp b/src/search.cpp
index c894403c..c44d150f 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -286,6 +286,7 @@ namespace {
   bool ok_to_prune(const Position& pos, Move m, Move threat);
   bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
   Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
+  Depth calculate_reduction(double baseReduction, int moveCount, Depth depth, double reductionInhibitor);
   void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
   void update_killers(Move m, SearchStack& ss);
   void update_gains(const Position& pos, Move move, Value before, Value after);
@@ -999,6 +1000,7 @@ namespace {
 
             if (doFullDepthSearch)
             {
+                ss[0].reduction = Depth(0);
                 value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
 
                 if (value > alpha)
@@ -2679,6 +2681,20 @@ namespace {
       return defaultEval;
   }
 
+  // calculate_reduction() returns reduction in plies based on
+  // moveCount and depth. Reduction is always at least one ply.
+
+  Depth calculate_reduction(double baseReduction, int moveCount, Depth depth, double reductionInhibitor) {
+
+    double red = baseReduction + ln(moveCount) * ln(depth / 2) / reductionInhibitor;
+
+    if (red >= 1.0)
+        return Depth(int(floor(red * int(OnePly))));
+    else
+        return Depth(0);
+
+  }
+
   // update_history() registers a good move that produced a beta-cutoff
   // in history and marks as failures all the other moves of that ply.