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EBF/beta-cutoff/counter-move stats, script.c FPE fix.
No LMR, no counter-move-driven move ordering (both explored separately,
kept out for now -- counter-move measured worse, ~655->647 solved on
ecm879 @ sn=4M with a leaner tree beforehand). Futility pruning restored.
Verified: 647/879 solved, EBF 4.609 @ sn=4M; 684/879 solved, EBF 3.995
@ 20s/move, 1cpu, 256m hash (typhoon_baseline.log).
The counter-move table is still written and its stats still tracked
(dynamic.c) for diagnostic purposes, but generate.c no longer reads it
for move ordering, so it has no effect on search behavior in this
commit.
lmr_testing/ holds the in-flight graded-LMR + counter-move code (not
applied here) with notes on what was already tried and measured, so a
future session can resume without re-deriving it.
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Fixes a real pathology: checks along a long unbroken forcing line could
extend for free (net zero cost against the qsearch boundary), letting
tree size blow up multiple orders of magnitude on positions like a
near-all-check forced mate (ECM.089: 4.5B nodes / 31min at depth 12
before this change).
- Main-search check extension: gate on SEE soundness (a losing
sacrifice check gets a small consolation QUARTER_PLY instead of the
full bonus a sound check gets), and flatten the sound-check bonus to
a flat THREE_QUARTERS_PLY instead of a near-free ONE_PLY.
- Lower the qsearch entry threshold to match (THREE_QUARTERS_PLY
instead of ONE_PLY) so a lone check still buys one extra full-width
ply as before; root.c trims QUARTER_PLY off the per-iteration depth
budget so this doesn't add a blanket 1/4 ply to every search.
- Qsearch's own check-widening (QSearchFromCheckNoStandPat) now relies
on fCouldStandPat history plus a g_uIterateDepth/4 ceiling instead of
an unconditional per-check grant, and QPLIES_OF_NON_CAPTURE_CHECKS
moved from 1 to 2 to cover both "enter qsearch already in check" and
"opponent's reply is the first real check" cases with one baseline
window instead of ad hoc attacker-color tracking.
Net effect on ECM.089 (sn 4M canary): ~7.5x fewer nodes and ~4x less
time at depth 12 versus the original, unbounded behavior. Costs solve
count on the full ECM suite (879 pos, sn 4M): 650 baseline -> 636 here
-- expected and accepted, since ECM is unusually check-extension-heavy
tactics and not representative of real games. Self-play vs baseline
(1000 games, st 1) came back at B_SCORE=0.4955, ELO=-3.1+/-21.5 --
statistically neutral, confirming the fix costs nothing in real play.
Co-Authored-By: Claude Sonnet 5 <[email protected]>
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Late Move Reductions using a depth x movecount table (Ethereal-style
formula), gated off PV nodes and the ply directly below a PV node
(PLY_INFO.fIsPVNode), with magnitude-aware re-search on fail-high.
Verified node-for-node identical to the previously tested-good v7
binary on a canary position (sd 10) after reconstructing from a ZFS
snapshot of search.c/root.c/split.c taken just before that binary was
built.
Co-Authored-By: Claude Sonnet 5 <[email protected]>
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