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/book.c b/src/book.c
index b9cb694..eaa4c48 100755
--- a/src/book.c
+++ b/src/book.c
@@ -2974,7 +2974,7 @@ Return value:
                     pos = GetRootPosition();
                     InitializeSearcherContext(pos, ctx);
                     DumpPosition(pos);
-                    (void)Eval(ctx, -INFINITY, +INFINITY);
+                    (void)Eval(ctx, -INFINITY, +INFINITY, NULL);
                     Trace("King safeties: W=%d, B=%d\n",
                           ctx->sPlyInfo[ctx->uPly].iKingScore[WHITE],
                           ctx->sPlyInfo[ctx->uPly].iKingScore[BLACK]);