Remove use of half-ply reductions from LMR, Null-move, IID and

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 945f5bf25d9c9d88687e9a36e0ad3ff3285fe823..436b64382266e1e8b92144ce45b8b6431b9b9be4 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -127,17 +127,14 @@ void Search::init() {
   {
       double    pvRed = 0.00 + log(double(hd)) * log(double(mc)) / 3.00;
       double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
-      Reductions[1][1][hd][mc] = int8_t(   pvRed >= 1.0 ?    pvRed * int(ONE_PLY) : 0);
-      Reductions[0][1][hd][mc] = int8_t(nonPVRed >= 1.0 ? nonPVRed * int(ONE_PLY) : 0);
+      Reductions[1][1][hd][mc] = int8_t(   pvRed >= 1.0 ?    pvRed+0.5: 0)*int(ONE_PLY);
+      Reductions[0][1][hd][mc] = int8_t(nonPVRed >= 1.0 ? nonPVRed+0.5: 0)*int(ONE_PLY);
 
       Reductions[1][0][hd][mc] = Reductions[1][1][hd][mc];
       Reductions[0][0][hd][mc] = Reductions[0][1][hd][mc];
 
-      if (Reductions[0][0][hd][mc] > 2 * ONE_PLY)
+      if (Reductions[0][0][hd][mc] >= 2 * ONE_PLY)
           Reductions[0][0][hd][mc] += ONE_PLY;
-
-      else if (Reductions[0][0][hd][mc] > 1 * ONE_PLY)
-          Reductions[0][0][hd][mc] += ONE_PLY / 2;
   }
 
   // Init futility move count array
@@ -565,10 +562,8 @@ namespace {
         assert(eval - beta >= 0);
 
         // Null move dynamic reduction based on depth and value
-        Depth R =  3 * ONE_PLY
-                 + depth / 4
-                 + (abs(beta) < VALUE_KNOWN_WIN ? int(eval - beta) / PawnValueMg * ONE_PLY
-                                                : DEPTH_ZERO);
+        Depth R = (3 + (depth / 8 )) * ONE_PLY
+                 + std::min(int(eval - beta) / PawnValueMg, 3) * ONE_PLY;
 
         pos.do_null_move(st);
         (ss+1)->skipNullMove = true;
@@ -634,7 +629,7 @@ namespace {
         && (PvNode || ss->staticEval + 256 >= beta))
     {
         Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
-
+        d = (d / 2) * 2;  // Round to nearest full-ply
         ss->skipNullMove = true;
         search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d, true);
         ss->skipNullMove = false;
@@ -736,7 +731,7 @@ moves_loop: // When in check and at SpNode search starts from here
           Value rBeta = ttValue - int(depth);
           ss->excludedMove = move;
           ss->skipNullMove = true;
-          value = search<NonPV, false>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
+          value = search<NonPV, false>(pos, ss, rBeta - 1, rBeta, (depth / 4) * 2, cutNode);
           ss->skipNullMove = false;
           ss->excludedMove = MOVE_NONE;
 
@@ -823,12 +818,10 @@ moves_loop: // When in check and at SpNode search starts from here
       {
           ss->reduction = reduction<PvNode>(improving, depth, moveCount);
 
-          if (!PvNode && cutNode)
+          if (   (!PvNode && cutNode)
+              ||  History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
               ss->reduction += ONE_PLY;
 
-          else if (History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
-              ss->reduction += ONE_PLY / 2;
-
           if (move == countermoves[0] || move == countermoves[1])
               ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);