Replace ctx->uPositional with a data-calibrated Eval() return value.

uPositional was a per-thread EWMA of abs(material - true score) used to
size lazy-eval and futility margins. It was history-derived (reflecting
whatever recent, unrelated positions looked like) rather than derived
from the position actually being margined, and its update/consumption
was tangled with EVAL_HASH (now disabled).

Eval() now takes an optional SCORE *piPositional out-param and fills it
in on every return path: exact (abs(material-delta)) on a full eval,
or an estimate from a new EstimatePositionalScore() on a lazy exit.
EstimatePositionalScore()'s two terms (king-safety-defect-bucketed, and
a flat residual for mobility/passers/everything else) are calibrated
from ~1.6M measured full-eval samples (p90 of the actual swing), not
guessed -- an initial guessed version measurably regressed ECM solve
rate (630 vs a 650 baseline at sn=4M); the recalibrated version is back
at parity (649/879).

search.c's qsearch futility now reads the value Eval() just computed
instead of the stale/shared ctx field. Also removes QSearchInDangerNoStandPat
and SideCanStandPat, dead since the danger-hash check that fed them was
already commented out (e08387a) -- they depended on the same enprise/
trapped-piece data this conversation is about to move off of
g_PositionHash entirely.

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

1 files changed, 4 insertions, 4 deletions

diff --git a/src/chess.h b/src/chess.h
index fe5cd2b..d6d4fa4 100755
--- a/src/chess.h
+++ b/src/chess.h
@@ -2565,9 +2565,6 @@ GetEnpriseCount(POSITION *pos, ULONG uSide);
 COOR
 GetTrappedPiece(POSITION *pos, ULONG uSide);
 
-FLAG
-SideCanStandPat(POSITION *pos, ULONG uSide);
-
 ULONG
 ValueOfMaterialInTroubleDespiteMove(POSITION *pos, ULONG uSide);
 
@@ -2593,6 +2590,9 @@ PawnHashLookup(SEARCHER_THREAD_CONTEXT *ctx);
 //
 #define LAZY_EVAL
 #define LAZE_EVAL_BASE_SCORE 10
+#define LAZY_EVAL_BASE_MARGIN (75) // cheap material-only lazy exit margin;
+                                    // widened by EstimatePositionalScore
+                                    // if this isn't enough on its own
 extern const int g_iAhead[2];
 extern const int g_iBehind[2];
 
@@ -2614,7 +2614,7 @@ ReadEvalDNA(char *szFilename);
 
 
 SCORE
-Eval(SEARCHER_THREAD_CONTEXT *, SCORE, SCORE);
+Eval(SEARCHER_THREAD_CONTEXT *, SCORE, SCORE, SCORE *);
 
 FLAG
 EvalPasserRaces(POSITION *,