Remove razoring

has become ineffective now.

STC https://tests.stockfishchess.org/tests/view/5fe653403932f79192d3981a
LLR: 2.95 (-2.94,2.94) {-1.25,0.25}
Total: 63448 W: 5965 L: 5934 D: 51549
Ptnml(0-2): 230, 4738, 21769, 4745, 242

LTC https://tests.stockfishchess.org/tests/view/5fe6f0f03932f79192d39856
LLR: 2.93 (-2.94,2.94) {-0.75,0.25}
Total: 65368 W: 2485 L: 2459 D: 60424
Ptnml(0-2): 33, 2186, 28230, 2192, 43

closes https://github.com/official-stockfish/Stockfish/pull/3278

bench: 4493379

diff --git a/src/search.cpp b/src/search.cpp
index b96efad09aa615af0dd6fda0db756dcaef402905..e2c3f584eedc53201fac6d06c33e184e0dae4b14 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -62,8 +62,7 @@ namespace {
   constexpr uint64_t TtHitAverageWindow     = 4096;
   constexpr uint64_t TtHitAverageResolution = 1024;
 
   constexpr uint64_t TtHitAverageWindow     = 4096;
   constexpr uint64_t TtHitAverageResolution = 1024;
 

-  // Razor and futility margins
-  constexpr int RazorMargin = 510;
+  // Futility margin

   Value futility_margin(Depth d, bool improving) {
     return Value(234 * (d - improving));
   }
   Value futility_margin(Depth d, bool improving) {
     return Value(234 * (d - improving));
   }


@@ -822,12 +821,6 @@ namespace {
         thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
     }
 
         thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
     }
 

-    // Step 7. Razoring (~1 Elo)
-    if (   !rootNode // The required rootNode PV handling is not available in qsearch
-        &&  depth == 1
-        &&  eval <= alpha - RazorMargin)
-        return qsearch<NT>(pos, ss, alpha, beta);
-

     // Set up improving flag that is used in various pruning heuristics
     // We define position as improving if static evaluation of position is better
     // Than the previous static evaluation at our turn
     // Set up improving flag that is used in various pruning heuristics
     // We define position as improving if static evaluation of position is better
     // Than the previous static evaluation at our turn


@@ -836,14 +829,14 @@ namespace {
                ? ss->staticEval > (ss-4)->staticEval || (ss-4)->staticEval == VALUE_NONE
                : ss->staticEval > (ss-2)->staticEval;
 
                ? ss->staticEval > (ss-4)->staticEval || (ss-4)->staticEval == VALUE_NONE
                : ss->staticEval > (ss-2)->staticEval;
 

-    // Step 8. Futility pruning: child node (~50 Elo)
+    // Step 7. Futility pruning: child node (~50 Elo)

     if (   !PvNode
         &&  depth < 9
         &&  eval - futility_margin(depth, improving) >= beta
         &&  eval < VALUE_KNOWN_WIN) // Do not return unproven wins
         return eval;
 
     if (   !PvNode
         &&  depth < 9
         &&  eval - futility_margin(depth, improving) >= beta
         &&  eval < VALUE_KNOWN_WIN) // Do not return unproven wins
         return eval;
 

-    // Step 9. Null move search with verification search (~40 Elo)
+    // Step 8. Null move search with verification search (~40 Elo)

     if (   !PvNode
         && (ss-1)->currentMove != MOVE_NULL
         && (ss-1)->statScore < 22977
     if (   !PvNode
         && (ss-1)->currentMove != MOVE_NULL
         && (ss-1)->statScore < 22977


@@ -895,7 +888,7 @@ namespace {
 
     probCutBeta = beta + 194 - 49 * improving;
 
 
     probCutBeta = beta + 194 - 49 * improving;
 

-    // Step 10. ProbCut (~10 Elo)
+    // Step 9. ProbCut (~10 Elo)

     // If we have a good enough capture and a reduced search returns a value
     // much above beta, we can (almost) safely prune the previous move.
     if (   !PvNode
     // If we have a good enough capture and a reduced search returns a value
     // much above beta, we can (almost) safely prune the previous move.
     if (   !PvNode


@@ -968,7 +961,7 @@ namespace {
          ss->ttPv = ttPv;
     }
 
          ss->ttPv = ttPv;
     }
 

-    // Step 11. If the position is not in TT, decrease depth by 2
+    // Step 10. If the position is not in TT, decrease depth by 2

     if (   PvNode
         && depth >= 6
         && !ttMove)
     if (   PvNode
         && depth >= 6
         && !ttMove)


@@ -997,7 +990,7 @@ moves_loop: // When in check, search starts from here
     // Mark this node as being searched
     ThreadHolding th(thisThread, posKey, ss->ply);
 
     // Mark this node as being searched
     ThreadHolding th(thisThread, posKey, ss->ply);
 

-    // Step 12. Loop through all pseudo-legal moves until no moves remain
+    // Step 11. Loop through all pseudo-legal moves until no moves remain

     // or a beta cutoff occurs.
     while ((move = mp.next_move(moveCountPruning)) != MOVE_NONE)
     {
     // or a beta cutoff occurs.
     while ((move = mp.next_move(moveCountPruning)) != MOVE_NONE)
     {


@@ -1035,7 +1028,7 @@ moves_loop: // When in check, search starts from here
       // Calculate new depth for this move
       newDepth = depth - 1;
 
       // Calculate new depth for this move
       newDepth = depth - 1;
 

-      // Step 13. Pruning at shallow depth (~200 Elo)
+      // Step 12. Pruning at shallow depth (~200 Elo)

       if (  !rootNode
           && pos.non_pawn_material(us)
           && bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
       if (  !rootNode
           && pos.non_pawn_material(us)
           && bestValue > VALUE_TB_LOSS_IN_MAX_PLY)


@@ -1083,7 +1076,7 @@ moves_loop: // When in check, search starts from here
           }
       }
 
           }
       }
 

-      // Step 14. Extensions (~75 Elo)
+      // Step 13. Extensions (~75 Elo)

 
       // 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),
 
       // 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),


@@ -1155,10 +1148,10 @@ moves_loop: // When in check, search starts from here
                                                                 [movedPiece]
                                                                 [to_sq(move)];
 
                                                                 [movedPiece]
                                                                 [to_sq(move)];
 

-      // Step 15. Make the move
+      // Step 14. Make the move

       pos.do_move(move, st, givesCheck);
 
       pos.do_move(move, st, givesCheck);
 

-      // Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
+      // Step 15. 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
       // re-searched at full depth.
       if (    depth >= 3
           &&  moveCount > 1 + 2 * rootNode


@@ -1258,7 +1251,7 @@ moves_loop: // When in check, search starts from here
           didLMR = false;
       }
 
           didLMR = false;
       }
 

-      // Step 17. Full depth search when LMR is skipped or fails high
+      // Step 16. Full depth search when LMR is skipped or fails high

       if (doFullDepthSearch)
       {
           value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
       if (doFullDepthSearch)
       {
           value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);


@@ -1285,12 +1278,12 @@ moves_loop: // When in check, search starts from here
                               std::min(maxNextDepth, newDepth), false);
       }
 
                               std::min(maxNextDepth, newDepth), false);
       }
 

-      // Step 18. Undo move
+      // Step 17. Undo move

       pos.undo_move(move);
 
       assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
 
       pos.undo_move(move);
 
       assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
 

-      // Step 19. Check for a new best move
+      // Step 18. Check for a new best move

       // Finished searching the move. If a stop occurred, the return value of
       // the search cannot be trusted, and we return immediately without
       // updating best move, PV and TT.
       // Finished searching the move. If a stop occurred, the return value of
       // the search cannot be trusted, and we return immediately without
       // updating best move, PV and TT.


@@ -1367,7 +1360,7 @@ moves_loop: // When in check, search starts from here
         return VALUE_DRAW;
     */
 
         return VALUE_DRAW;
     */
 

-    // Step 20. Check for mate and stalemate
+    // Step 19. Check for mate and stalemate

     // All legal moves have been searched and if there are no legal moves, it
     // must be a mate or a stalemate. If we are in a singular extension search then
     // return a fail low score.
     // All legal moves have been searched and if there are no legal moves, it
     // must be a mate or a stalemate. If we are in a singular extension search then
     // return a fail low score.