Rework check/pawn-push/recapture extension gating on real SEE (GetMoveSee, generalized from GetCheckSee), restrict LMR to leftover moves only, and tighten recapture's window back to 1x after measuring a 6.8x node blowup from sharing the wider window.

Head-to-head match at 1170 games confirms parity with the prior head (score=0.510, LLR still between bounds) -- landing as a neutral-or-better baseline rather than a regression.

1 files changed, 15 insertions, 6 deletions

diff --git a/src/split.c b/src/split.c
index 3a69ab4..679d26d 100644
--- a/src/split.c
+++ b/src/split.c
@@ -1081,7 +1081,7 @@ Return value:
     INT iOrigExtend;
     INT iExtend;
     MOVE mv;
-    SCORE iCheckSee;
+    SCORE iMoveSee;
 #ifdef DEBUG
     POSITION board;
 
@@ -1120,10 +1120,11 @@ Return value:
         ASSERT(iExtend <= +ONE_PLY);
 
         // SEE on the PRE-move position -- see search.c's identical comment.
-        iCheckSee = 0;
-        if (IS_CHECKING_MOVE(mv))
+        iMoveSee = 0;
+        if (IS_CHECKING_MOVE(mv) ||
+            (mv.pCaptured && !IS_PAWN(mv.pCaptured) && (uDepth <= THREE_PLY)))
         {
-            iCheckSee = GetCheckSee(ctx,
+            iMoveSee = GetMoveSee(ctx,
                                     mv,
                                     ctx->sMoveStack.uBegin[ctx->uPly] +
                                         uMoveNum);
@@ -1134,14 +1135,22 @@ Return value:
             ASSERT((IS_CHECKING_MOVE(mv) && InCheck(&ctx->sPosition, ctx->sPosition.uToMove)) ||
                    (!IS_CHECKING_MOVE(mv) && !InCheck(&ctx->sPosition, ctx->sPosition.uToMove)));
 
-            // Compute extension
+            // Compute extension. fIsLeftoverMove is unconditionally TRUE
+            // here: search.c only ever starts a split when the move it
+            // was about to try was itself already classified as a
+            // leftover move (see its own fIsLeftoverMove-gated split
+            // condition) -- every move HelpSearch pulls from the shared
+            // pool for that split is drawn from that same leftover
+            // range, so there's no "early, well-ordered move" case to
+            // distinguish here.
             ComputeMoveExtension(ctx,
                                  iAlpha,
                                  iBeta,
                                  (ctx->sMoveStack.uBegin[ctx->uPly - 1] + uMoveNum),
                                  iEval,
                                  uDepth,
-                                 iCheckSee,
+                                 iMoveSee,
+                                 TRUE,
                                  &iExtend);
 
             //