Remove dead EFP references left over from its removal

EFP (extended futility pruning) was removed from Search()'s move loop
in favor of LMP's joint FH% table, but several comments, a dead
counter (u64EFPPruned, never incremented anywhere), and two unused
defines (EFP_FH_MIN_SAMPLES/EFP_FH_PRUNE_THRESHOLD_PCT_THOUSANDTHS)
were left behind claiming EFP still gates something. Clean these up:

- Delete u64EFPPruned (COUNTERS and g_Options) and its dead
  reader/writer in root.c.
- Delete the two unused EFP_FH_* defines in search.c, and the stale
  fAnyMoveEFPPruned comment describing a branch that no longer
  skips a store.
- Fix dangling prose references to EFP in generate.c, chess.h,
  searchsup.c, and testsearch.c that describe present-tense behavior
  EFP no longer participates in, preserving the historical rationale
  where it's still relevant (e.g. why EstimateHangingMaterialCp can
  return a negative value).

Deliberately left alone (flagged for a separate decision, not a
clear delete): script.c's still-live JOINT_EXTRA_VERIFY calibration
labels ("EFP tier1/tier2"), search.c's _PostReduceDepthBucketEfpAligned
(same live mechanism, name only), searchsup.c's LMP_BASE_MOVENUM/
LMP_PER_PLY_MOVENUM dead macros (kept pending a real floor/ceiling
decision), and PLY_INFO.iPositional[2] (now write-only, but removing
it touches Eval()'s call signature everywhere).

Comment/dead-code only, no logic touched.

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

1 files changed, 0 insertions, 15 deletions

diff --git a/src/search.c b/src/search.c
index 3abb44b..d0d67b9 100644
--- a/src/search.c
+++ b/src/search.c
@@ -75,15 +75,6 @@ extern FLAG g_fCanSplit[MAX_PLY_PER_SEARCH];
 #define PREPARE_TO_TRY_MOVES  (2)
 #define TRY_GENERATED_MOVES   (3)
 
-// EFP's fail-high-history exemption: below EFP_FH_MIN_SAMPLES
-// observations, GetMoveFailHighPctThousandths's result isn't trusted
-// enough to override the static-eval-based decision either way.
-// THOUSANDTHS, not whole percent, since 2026-10-02's rename -- 100
-// thousandths == 10%, unchanged in effect from the old whole-percent
-// EFP_FH_PRUNE_THRESHOLD of 10.
-#define EFP_FH_MIN_SAMPLES                (5)
-#define EFP_FH_PRUNE_THRESHOLD_PCT_THOUSANDTHS (10000)  // 10%
-
 // 2026-10-13: "skip trying null-move at all" on the iEval <= iAlpha
 // side (alpha-side table, EV-neutral -- the real move loop still runs
 // and finds the correct score either way; we only forgo the cheap
@@ -1848,12 +1839,6 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
         //                                            --Ed Schroder
         StoreUpperBound(pos, iBestScore, uDepth, fThreat);
     }
-    // else: fail-low (iAlpha == iInitialAlpha) AND fAnyMoveEFPPruned --
-    // no sound bound in either direction to store (the skipped move
-    // could have raised the true value above iBestScore, so it's not a
-    // valid upper bound; there's no mvBest to offer as a lower bound
-    // either, since nothing beat alpha). Store nothing rather than
-    // cache an unsound result.
 
  end:
     ASSERT(IS_VALID_SCORE(iBeta));