Add 5D FH% joint table (improve axis) + beta-side static-null-move

table, wire up static null-move pruning; misc searchsup.c tuning;
--cpus=4 fix; multi-pool match_play.py openings.

data.c: g_uJointFHThousandths grows a 5th "improve" axis
([12][11][11][15] -> [12][11][11][16][11]); new
g_uBetaFHThousandths[12][21][11][11] table added. chess.h/searchsup.c/
search.c/split.c: minimal consumer wiring for the improve axis
(ImproveBucket(), extended _JointTablePredictedFHThousandths
signature/callers).

search.c: new static (score-only, no verification search) null-move
cutoff ahead of the existing real null-move check -- when iEval > iBeta
by enough that the new beta-side table predicts a real null-move
search would fail high with >95% confidence, take the cutoff on the
table's say-so instead of paying for the verification search.

searchsup.c: EstimateHangingMaterialCp now gives half credit when the
mover has an unrelated piece already flagged trapped at node entry;
bumped the SEE>=0 check extension from 3/4 ply to a full ply when the
opponent has significant material left; removed the "entering the
endgame extension" bonus (recapture extension and its window check
untouched).

main.c: accept "--opt=value" in addition to "--opt value" on the
command line (a bare "--cpus=4" used to silently fail to match and
leave uNumProcessors at its default of 1); also fixes a latent
off-by-one that could read one past the end of argv for a value-taking
flag given as the last command-line argument.

unix.c: brace-scoping cleanup around signal handler setup, no behavior
change.

eval_tune/match_play.py, test_vs_head.sh: sample opening positions from
multiple PGN pools (twic_filtered.pgn + lichess*.pgn) instead of one,
for more opening diversity in match-play testing.

Brought out of a larger stashed changeset one piece at a time, each
verified independently against a --cpus 1 / --cpus 4 ratio benchmark
to rule out the MP scaling regression that changeset originally
triggered (see SCOTT_IS_A_MORON.md) -- no regression reproduced in any
of the pieces here. Playing-strength impact measured as neutral via
self-play (170 games, llr=-0.04, score=0.500) despite ~1 ply deeper
average search. The stashed changeset's EFP margin rewrite, LMP
threshold rewrite, and a disabled null-move-skip experiment are
deliberately excluded -- those need their own careful, separate
commits and testing. The stash's eval.c retuning is abandoned (measured
~even/worse over a ~700-game overnight self-play run).

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

1 files changed, 48 insertions, 3 deletions

diff --git a/src/chess.h b/src/chess.h
index 7e37245..91c6a0c 100755
--- a/src/chess.h
+++ b/src/chess.h
@@ -1007,6 +1007,24 @@ MOVE_STACK;
 #define GAP_CP_BUCKET_WIDTH (100)
 #define GAP_CP_BUCKETS (11)
 
+// 2026-10-10: "improving" axis -- does (iEval - iEval two plies ago,
+// same side to move) predict FH%? Signed and genuinely two-sided, so
+// a symmetric 100cp-wide-bin shape around a center "no real change"
+// bucket (index 5), with overflow buckets at both tails, matching
+// HANG/GAP's own 11-bucket count. Added as g_uJointFHThousandths's
+// 5th (trailing) axis -- see data.c.
+#define IMPROVE_BUCKET_WIDTH (100)
+#define IMPROVE_BUCKETS (11)
+#define IMPROVE_CP_CENTER_WIDTH (100) // center bucket covers (-100, 100)
+
+// 2026-10-10: gap-above-beta, for the beta-side static-NM table --
+// gated on iEval > iBeta, so always >= 0, no symmetric/center bucket
+// needed. Plain 100cp-wide bins from 0, wide enough (2000cp) to find
+// where FH% actually saturates toward ~100%, with an overflow bucket
+// past that.
+#define GAP_BETA_BUCKET_WIDTH (100)
+#define GAP_BETA_BUCKETS (21) // 0-99 .. 1900-1999, 20 == 2000cp+ overflow
+
 // 2026-09-28: the "late axis" -- this move's own 1-based ordinal
 // position in the list of moves actually tried at this node
 // (uLegalMoves, right after MakeMove succeeds). Direct, unpaired
@@ -1094,7 +1112,8 @@ MOVE_STACK;
 // COST of a wrong prune scales with remaining depth even where the rate
 // does not.
 // Shipped depth dimension of g_uJointFHThousandths (data.c declares it
-// as [12][11][11][15]; the 12 is _ShipDepthBucket's range).
+// as [12][11][11][16][11], including the 5th/improve axis; the 12 is
+// _ShipDepthBucket's range).
 #define SHIP_DEPTH_BUCKETS (12)
 #define PRUNE_VERIFY_BANDS (8)
 // band edges, predicted FH in thousandths of a percent:
@@ -1330,6 +1349,13 @@ typedef struct _COUNTERS
 #endif
         UINT64 u64NullMoves;
         UINT64 u64NullMoveSuccess;
+
+        // 2026-10-10: static (score-only, no verification search)
+        // null-move cutoff, gated on iEval > iBeta and the beta-side
+        // FH% table (g_uBetaFHThousandths) predicting a cutoff with
+        // >95% confidence -- see search.c's fTryBetaPruningHere block.
+        UINT64 u64QuickNullMoves;
+        UINT64 u64QuickNullMoveSuccess;
 #ifdef TEST_NULL
         // Precision/recall calibration for the null-move try/avoid
         // decision. Indexed by _NullCalibBucketIndex() (search.c).
@@ -3299,7 +3325,13 @@ extern BITBOARD g_KingAttacksBB[128];
 // depth outermost for cache locality -- a whole node's move loop shares
 // one depth-slice (11*11*15 = 1,815 cells, ~3.5KB). Not yet consumed by
 // search.c -- phase 2 (LMR replacement) is a separate, later step.
-extern USHORT g_uJointFHThousandths[12][11][11][15];
+extern USHORT g_uJointFHThousandths[12][11][11][16][11];
+
+// 2026-10-10: beta-side (static-null-move) 4D FH% table -- see data.c's
+// header. [depth][gapBeta][ownImprove][enemyImprove]. Cell stores the
+// GAP TO 100% FH rate (thousandths of a percentage point), not FH%
+// itself -- see _BetaTablePredictedFHThousandths's comment for why.
+extern USHORT g_uBetaFHThousandths[12][21][11][11];
 
 // 2026-09-15: king-ring bitboard split for _EvalKing's linear-SCORE
 // rewrite -- front/back mirror EmptyAttackedSquare's old color-dependent
@@ -3857,11 +3889,24 @@ MoveNumBucket(ULONG uMoveNum);
 ULONG
 DepthBucket(ULONG uCandDepth);
 
+ULONG
+ImproveBucket(SCORE iImprovement);
+
+ULONG
+GapBetaBucket(SCORE iGapBeta);
+
 USHORT
 _JointTablePredictedFHThousandths(IN ULONG uRawDepthBucket,
                                    IN ULONG uRawDumbBucket,
                                    IN ULONG uRawGapBucket,
-                                   IN ULONG uRawLateBucket);
+                                   IN ULONG uRawLateBucket,
+                                   IN ULONG uRawImproveBucket);
+
+ULONG
+_BetaTablePredictedFHThousandths(IN ULONG uRawDepthBucket,
+                                  IN ULONG uGapBetaBucket,
+                                  IN ULONG uOwnImproveBucket,
+                                  IN ULONG uEnemyImproveBucket);
 
 FLAG
 WeShouldTryNullmovePruning(IN SEARCHER_THREAD_CONTEXT *ctx,