Make razor margin depth independent

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index ed01e0dee04c89d4f31dd29264ad576a441df89f..214177a2afae1280eb296352fe59245dfd2c98cb 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -2,7 +2,7 @@
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
-  Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -67,8 +67,7 @@ namespace {
   const int skipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
 
   // Razoring and futility margin based on depth
-  // razor_margin[0] is unused as long as depth >= ONE_PLY in search
-  const int razor_margin[] = { 0, 570, 603, 554 };
+  const int razor_margin = 600;
   Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); }
 
   // Futility and reductions lookup tables, initialized at startup
@@ -173,13 +172,7 @@ void Search::clear() {
 
   Time.availableNodes = 0;
   TT.clear();
-
-  for (Thread* th : Threads)
-      th->clear();
-
-  Threads.main()->callsCnt = 0;
-  Threads.main()->previousScore = VALUE_INFINITE;
-  Threads.main()->previousTimeReduction = 1;
+  Threads.clear();
 }
 
 
@@ -557,7 +550,7 @@ namespace {
     // search to overwrite a previous full search TT value, so we use a different
     // position key in case of an excluded move.
     excludedMove = ss->excludedMove;
-    posKey = pos.key() ^ Key(excludedMove);
+    posKey = pos.key() ^ Key(excludedMove << 16); // isn't a very good hash
     tte = TT.probe(posKey, ttHit);
     ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
     ttMove =  rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0]
@@ -660,12 +653,12 @@ namespace {
     // Step 6. Razoring (skipped when in check)
     if (   !PvNode
         &&  depth < 4 * ONE_PLY
-        &&  eval + razor_margin[depth / ONE_PLY] <= alpha)
+        &&  eval + razor_margin <= alpha)
     {
         if (depth <= ONE_PLY)
             return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
 
-        Value ralpha = alpha - razor_margin[depth / ONE_PLY];
+        Value ralpha = alpha - razor_margin;
         Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
         if (v <= ralpha)
             return v;
@@ -681,7 +674,8 @@ namespace {
     // Step 8. Null move search with verification search (is omitted in PV nodes)
     if (   !PvNode
         &&  eval >= beta
-        &&  ss->staticEval >= beta - 36 * depth / ONE_PLY + 225)
+        &&  ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
+        && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
     {
 
         assert(eval - beta >= 0);
@@ -703,13 +697,19 @@ namespace {
             if (nullValue >= VALUE_MATE_IN_MAX_PLY)
                 nullValue = beta;
 
-            if (depth < 12 * ONE_PLY && abs(beta) < VALUE_KNOWN_WIN)
+            if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_ply))
                 return nullValue;
 
             // Do verification search at high depths
+            // disable null move pruning for side to move for the first part of the remaining search tree
+            thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4;
+            thisThread->nmp_odd = ss->ply % 2;
+
             Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta)
                                         :  search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
 
+            thisThread->nmp_odd = thisThread->nmp_ply = 0;
+
             if (v >= beta)
                 return nullValue;
         }
@@ -1251,7 +1251,6 @@ moves_loop: // When in check search starts from here
 
       // Don't search moves with negative SEE values
       if (  (!InCheck || evasionPrunable)
-          &&  type_of(move) != PROMOTION
           &&  !pos.see_ge(move))
           continue;
 
@@ -1493,7 +1492,7 @@ moves_loop: // When in check search starts from here
     if (Threads.ponder)
         return;
 
-    if (   (Limits.use_time_management() && elapsed > Time.maximum())
+    if (   (Limits.use_time_management() && elapsed > Time.maximum() - 10)
         || (Limits.movetime && elapsed >= Limits.movetime)
         || (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes))
             Threads.stop = true;