Update Elo estimates for terms in search

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index b0bcc57a44ee05f8f71fe2205d187f25622613fb..6146bdf6b5ae9ac24f48cb2e3e3ca831bf8f7618 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) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2020 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
@@ -716,7 +716,9 @@ namespace {
                 update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty);
             }
         }
-        return ttValue;
+
+        if (pos.rule50_count() < 90)
+            return ttValue;
     }
 
     // Step 5. Tablebases probe
@@ -806,7 +808,7 @@ namespace {
         tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
     }
 
-    // Step 7. Razoring (~2 Elo)
+    // Step 7. Razoring (~1 Elo)
     if (   !rootNode // The required rootNode PV handling is not available in qsearch
         &&  depth < 2
         &&  eval <= alpha - RazorMargin)
@@ -815,7 +817,7 @@ namespace {
     improving =  (ss-2)->staticEval == VALUE_NONE ? (ss->staticEval >= (ss-4)->staticEval
               || (ss-4)->staticEval == VALUE_NONE) : ss->staticEval >= (ss-2)->staticEval;
 
-    // Step 8. Futility pruning: child node (~30 Elo)
+    // Step 8. Futility pruning: child node (~50 Elo)
     if (   !PvNode
         &&  depth < 6
         &&  eval - futility_margin(depth, improving) >= beta
@@ -825,10 +827,10 @@ namespace {
     // Step 9. Null move search with verification search (~40 Elo)
     if (   !PvNode
         && (ss-1)->currentMove != MOVE_NULL
-        && (ss-1)->statScore < 23405
+        && (ss-1)->statScore < 23397
         &&  eval >= beta
         &&  eval >= ss->staticEval
-        &&  ss->staticEval >= beta - 32 * depth + 317 - improving * 30
+        &&  ss->staticEval >= beta - 32 * depth + 292 - improving * 30
         && !excludedMove
         &&  pos.non_pawn_material(us)
         && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
@@ -915,7 +917,7 @@ namespace {
             }
     }
 
-    // Step 11. Internal iterative deepening (~2 Elo)
+    // Step 11. Internal iterative deepening (~1 Elo)
     if (depth >= 7 && !ttMove)
     {
         search<NT>(pos, ss, alpha, beta, depth - 7, cutNode);
@@ -980,7 +982,7 @@ moves_loop: // When in check, search starts from here
       // Calculate new depth for this move
       newDepth = depth - 1;
 
-      // Step 13. Pruning at shallow depth (~170 Elo)
+      // Step 13. Pruning at shallow depth (~200 Elo)
       if (  !rootNode
           && pos.non_pawn_material(us)
           && bestValue > VALUE_MATED_IN_MAX_PLY)
@@ -1000,23 +1002,27 @@ moves_loop: // When in check, search starts from here
                   && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
                   continue;
 
-              // Futility pruning: parent node (~2 Elo)
+              // Futility pruning: parent node (~5 Elo)
               if (   lmrDepth < 6
                   && !inCheck
-                  && ss->staticEval + 255 + 182 * lmrDepth <= alpha)
+                  && ss->staticEval + 255 + 182 * lmrDepth <= alpha
+                  &&  thisThread->mainHistory[us][from_to(move)]
+                    + (*contHist[0])[movedPiece][to_sq(move)]
+                    + (*contHist[1])[movedPiece][to_sq(move)]
+                    + (*contHist[3])[movedPiece][to_sq(move)] < 30000)
                   continue;
 
-              // Prune moves with negative SEE (~10 Elo)
+              // Prune moves with negative SEE (~20 Elo)
               if (!pos.see_ge(move, Value(-(32 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
                   continue;
           }
-          else if (!pos.see_ge(move, Value(-194) * depth)) // (~20 Elo)
+          else if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo)
                   continue;
       }
 
-      // Step 14. Extensions (~70 Elo)
+      // Step 14. Extensions (~75 Elo)
 
-      // Singular extension search (~60 Elo). If all moves but one fail low on a
+      // Singular extension search (~70 Elo). If all moves but one fail low on a
       // search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
       // then that move is singular and should be extended. To verify this we do
       // a reduced search on all the other moves but the ttMove and if the
@@ -1095,7 +1101,7 @@ moves_loop: // When in check, search starts from here
       // Step 15. Make the move
       pos.do_move(move, st, givesCheck);
 
-      // Step 16. Reduced depth search (LMR). If the move fails high it will be
+      // Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
       // re-searched at full depth.
       if (    depth >= 3
           &&  moveCount > 1 + 2 * rootNode
@@ -1116,31 +1122,31 @@ moves_loop: // When in check, search starts from here
           if (th.marked())
               r++;
 
-          // Decrease reduction if position is or has been on the PV
+          // Decrease reduction if position is or has been on the PV (~10 Elo)
           if (ttPv)
               r -= 2;
 
-          // Decrease reduction if opponent's move count is high (~10 Elo)
+          // Decrease reduction if opponent's move count is high (~5 Elo)
           if ((ss-1)->moveCount > 14)
               r--;
 
-          // Decrease reduction if ttMove has been singularly extended
+          // Decrease reduction if ttMove has been singularly extended (~3 Elo)
           if (singularLMR)
               r -= 2;
 
           if (!captureOrPromotion)
           {
-              // Increase reduction if ttMove is a capture (~0 Elo)
+              // Increase reduction if ttMove is a capture (~5 Elo)
               if (ttCapture)
                   r++;
 
-              // Increase reduction for cut nodes (~5 Elo)
+              // Increase reduction for cut nodes (~10 Elo)
               if (cutNode)
                   r += 2;
 
               // Decrease reduction for moves that escape a capture. Filter out
               // castling moves, because they are coded as "king captures rook" and
-              // hence break make_move(). (~5 Elo)
+              // hence break make_move(). (~2 Elo)
               else if (    type_of(move) == NORMAL
                        && !pos.see_ge(reverse_move(move)))
                   r -= 2;