More aggressive move reductions; Wilson bound overrides static signal when available

SPRT playtest (2000 games, sd/depth matched): -535 =875 +590, score=0.514,
llr=+1.04 (floated around +1.0 the whole run, never went negative) toward
H1=+2.94. Not a confirmed win, but searches meaningfully deeper (avg depth
14.35 vs 13.50, EBF 3.131 vs 3.305) at no measurable strength cost -- worth
banking and continuing to accumulate games against.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/chess.h b/src/chess.h
index 189e0a4..05052c6 100755
--- a/src/chess.h
+++ b/src/chess.h
@@ -1187,6 +1187,18 @@ typedef struct _COUNTERS
         UINT64 u64LeftoverTries;       // leftover (sub-GOOD_MOVE) move tried
         UINT64 u64LeftoverAlpha;       // ...raised alpha (didn't fail high)
         UINT64 u64LeftoverFH;          // ...failed high
+#ifdef HASHCAP_COLLECTION
+        // 2026-10-23, one-off measurement: P(leftover move fails high |
+        // hash move at this node was a capture, node type guess). See
+        // GNUmakefile's HASHCAP_COLLECTION comment for what's being
+        // measured and why -- not a permanent production signal, this
+        // is purely to find out whether IS_CAPTURE(mvHash) (optionally
+        // && eNodeType==NODE_CUT) is worth baking into the joint table
+        // as a real axis before building anything around it.
+        // Indexed [fHashMoveIsCapture][eNodeType==NODE_CUT].
+        UINT64 u64HashCapTries[2][2];
+        UINT64 u64HashCapFH[2][2];
+#endif
         UINT64 u64CMEvidenceTries[CM_EVIDENCE_BUCKETS];
         UINT64 u64CMEvidenceFH[CM_EVIDENCE_BUCKETS];
         UINT64 u64HangEstimateTries[HANG_CP_BUCKETS];
@@ -1759,6 +1771,16 @@ typedef struct _PLY_INFO
     MOVE mvBest;
     MOVE PV[MAX_PLY_PER_SEARCH];
 
+    // 2026-10-23, one-off diagnostic support: was the hash move at
+    // THIS node a capture/promotion? Set once per node, right after
+    // mvHash is established (search.c), read back by SearchOneMove
+    // (searchsup.c) to bucket the HASHCAP_COLLECTION measurement --
+    // see that macro's own comment (GNUmakefile) for what it's
+    // measuring and why. FALSE (not just unset) whenever there was no
+    // hash move at all, same as IS_CAPTURE_OR_PROMOTION on a null move
+    // would read.
+    FLAG fHashMoveIsCapture;
+
     // Stamped with (pos->u64NonPawnSig ^ pos->u64PawnSig) the instant a
     // full (not lazy/super-lazy) Eval() call finishes for the position
     // currently sitting at this ply -- see Eval()'s own comment near
@@ -2229,6 +2251,10 @@ typedef struct _GAME_OPTIONS
     UINT64 u64LeftoverTries;
     UINT64 u64LeftoverAlpha;
     UINT64 u64LeftoverFH;
+#ifdef HASHCAP_COLLECTION
+    UINT64 u64HashCapTries[2][2];
+    UINT64 u64HashCapFH[2][2];
+#endif
     UINT64 u64CMEvidenceTries[CM_EVIDENCE_BUCKETS];
     UINT64 u64CMEvidenceFH[CM_EVIDENCE_BUCKETS];
     UINT64 u64HangEstimateTries[HANG_CP_BUCKETS];
@@ -4338,6 +4364,12 @@ extern SCORE g_iLMRQuietReduction[MAX_PLY_PER_SEARCH + 1][LMR_TABLE_MAX_MOVES +
 void
 InitializeLMRTable(void);
 
+void
+InitializeWilsonBoundTable(void);
+
+ULONG
+GetMoveFailHighWilsonUpperBoundThousandths(MOVE mv);
+
 FLAG
 CanWeReduceOrPruneMove(IN SEARCHER_THREAD_CONTEXT *ctx,
                     IN MOVE mv,