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, 1 insertions, 1 deletions

diff --git a/src/evalhash.c b/src/evalhash.c
index bd95b99..fc29b88 100644
--- a/src/evalhash.c
+++ b/src/evalhash.c
@@ -64,7 +64,7 @@ Return value:
 
     if (ctx->uPly <= 4)
     {
-        return Eval(ctx, iAlpha, iBeta);
+        return Eval(ctx, iAlpha, iBeta, NULL);
     }
 #ifdef EVAL_HASH
     else if ((fUseHash) || (ctx->uPly <= (g_uIterateDepth / 2)))