Retire null search verification

Tested with SPRT in simplification mode [-4.00,0.00],
this ensures that the patch is (very probably) not
a regression.

Passed both short TC
LLR: 2.95 (-2.94,2.94) [-4.00,0.00]
Total: 27543 W: 4278 L: 4209 D: 19056

And long TC
LLR: 2.95 (-2.94,2.94) [-4.00,0.00]
Total: 39483 W: 7325 L: 7305 D: 24853

bench: 8347121

diff --git a/src/search.cpp b/src/search.cpp
index 3e6e38bd1273e4a94e67c39403ffb5448d697610..6d900f7bb7ae673575f2d52b953ed63ca2c2d3ff 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -595,7 +595,7 @@ namespace {
     // Step 6. Razoring (skipped when in check)
     if (   !PvNode
         &&  depth < 4 * ONE_PLY
     // Step 6. Razoring (skipped when in check)
     if (   !PvNode
         &&  depth < 4 * ONE_PLY

-        &&  eval + razor_margin(depth) < beta
+        &&  eval + razor_margin(depth) <= alpha

         &&  ttMove == MOVE_NONE
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY
         && !pos.pawn_on_7th(pos.side_to_move()))
         &&  ttMove == MOVE_NONE
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY
         && !pos.pawn_on_7th(pos.side_to_move()))


@@ -640,24 +640,8 @@ namespace {
         (ss+1)->skipNullMove = false;
         pos.undo_null_move();
 
         (ss+1)->skipNullMove = false;
         pos.undo_null_move();
 

-        if (nullValue >= beta)
-        {
-            // Do not return unproven mate scores
-            if (nullValue >= VALUE_MATE_IN_MAX_PLY)
-                nullValue = beta;
-
-            if (depth < 12 * ONE_PLY)
-                return nullValue;
-
-            // Do verification search at high depths
-            ss->skipNullMove = true;
-            Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta, DEPTH_ZERO)
-                                        :  search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
-            ss->skipNullMove = false;
-
-            if (v >= beta)
-                return nullValue;
-        }
+        if (nullValue >= beta) // Do not return unproven mate scores
+            return nullValue >= VALUE_MATE_IN_MAX_PLY ? beta : nullValue;

     }
 
     // Step 9. ProbCut (skipped when in check)
     }
 
     // Step 9. ProbCut (skipped when in check)