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, 0 insertions, 22 deletions

diff --git a/src/poshash.c b/src/poshash.c
index 19d10ab..d8b4fcd 100644
--- a/src/poshash.c
+++ b/src/poshash.c
@@ -185,28 +185,6 @@ GetTrappedPiece(POSITION *pos, ULONG uSide)
     return c;
 }
 
-FLAG
-SideCanStandPat(POSITION *pos, ULONG uSide)
-{
-    UINT64 u64Sig = PositionToSignatureIgnoringMove(pos);
-    ULONG uEntry = PositionSigToHashPosition(u64Sig);
-    POSITION_HASH_ENTRY *pHash = &(g_PositionHash[uEntry]);
-    FLAG fStand = TRUE;
-#ifdef MP
-    ULONG uLock = HashPositionToLockNumber(uEntry);
-    LOCK_POSITION_HASH(uLock);
-#endif
-    if (pHash->u64Sig == u64Sig)
-    {
-        fStand = ((pHash->cTrapped[uSide] == ILLEGAL_COOR) &&
-                  (pHash->uEnpriseCount[uSide] < 2));
-    }
-#ifdef MP
-    UNLOCK_POSITION_HASH(uLock);
-#endif
-    return fStand;
-}
-
 ULONG
 ValueOfMaterialInTroubleDespiteMove(POSITION *pos, ULONG uSide) 
 {