Remove noLMRExtension flag

This simplification patch removes the noLMRExtension flag. It was introduced in June
(see following link for that commit), but does not seem to be necessary anymore.
Link: https://github.com/official-stockfish/Stockfish/commit/e1f181ee643dcaa92c606b74b3abd23dede136cd
STC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 21200 W: 5369 L: 5228 D: 10603
Ptnml(0-2): 67, 2355, 5616, 2494, 68
https://tests.stockfishchess.org/tests/view/616c03d299b580bf37797dcb

LTC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 37536 W: 9387 L: 9278 D: 18871
Ptnml(0-2): 23, 3988, 10643, 4085, 29
https://tests.stockfishchess.org/tests/view/616c10f499b580bf37797ddd

closes https://github.com/official-stockfish/Stockfish/pull/3743

Bench: 4792969

diff --git a/src/search.cpp b/src/search.cpp
index 39bb1fdb94867728840b0653658da19645bb1de7..9a2bd41565911c1bd1179df7d074a20b72ed0846 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -588,7 +588,7 @@ namespace {
     Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
     bool givesCheck, improving, didLMR, priorCapture;
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
     Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
     bool givesCheck, improving, didLMR, priorCapture;
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning,

-         ttCapture, singularQuietLMR, noLMRExtension;
+         ttCapture, singularQuietLMR;

     Piece movedPiece;
     int moveCount, captureCount, quietCount, bestMoveCount, improvement;
 
     Piece movedPiece;
     int moveCount, captureCount, quietCount, bestMoveCount, improvement;
 


@@ -984,7 +984,7 @@ moves_loop: // When in check, search starts here
                                       ss->ply);
 
     value = bestValue;
                                       ss->ply);
 
     value = bestValue;

-    singularQuietLMR = moveCountPruning = noLMRExtension = false;
+    singularQuietLMR = moveCountPruning = false;

 
     // Indicate PvNodes that will probably fail low if the node was searched
     // at a depth equal or greater than the current depth, and the result of this search was a fail low.
 
     // Indicate PvNodes that will probably fail low if the node was searched
     // at a depth equal or greater than the current depth, and the result of this search was a fail low.


@@ -1108,10 +1108,7 @@ moves_loop: // When in check, search starts here
               if (   !PvNode
                   && value < singularBeta - 75
                   && ss->doubleExtensions <= 6)
               if (   !PvNode
                   && value < singularBeta - 75
                   && ss->doubleExtensions <= 6)

-              {

                   extension = 2;
                   extension = 2;

-                  noLMRExtension = true;
-              }

           }
 
           // Multi-cut pruning
           }
 
           // Multi-cut pruning


@@ -1221,7 +1218,6 @@ moves_loop: // When in check, search starts here
           // are really negative and movecount is low, we allow this move to be searched
           // deeper than the first move (this may lead to hidden double extensions).
           int deeper =   r >= -1                   ? 0
           // are really negative and movecount is low, we allow this move to be searched
           // deeper than the first move (this may lead to hidden double extensions).
           int deeper =   r >= -1                   ? 0

-                       : noLMRExtension            ? 0

                        : moveCount <= 3 && r <= -3 ? 2
                        : moveCount <= 5            ? 1
                        : PvNode && depth > 6       ? 1
                        : moveCount <= 3 && r <= -3 ? 2
                        : moveCount <= 5            ? 1
                        : PvNode && depth > 6       ? 1