Fix batch-mode exit code, killer-table backfill collision, impossible QSearch mate-magnitude asserts, MATEMOVE PV display, --command truncation, and test.sh's stale egtbpath.

Several small, independent correctness fixes bundled together since
they were all exercised together through today's precommit_check.sh
and curated-suite runs:

- command.c: batch-mode's "Exhausted input" exit was exit(-1), which
  truncates to 255 (an 8-bit status) and is indistinguishable from a
  real crash's nonzero exit. Changed to exit(0) so debug_smoke_test.sh
  can reliably tell a clean batch run apart from a crash by exit status
  alone.

- dynamic.c: _NewKillerMove's slot[1] backfill from
  mvNullmoveQuietRefutations[uPly] had no check that the backfilled
  move differed from the move just placed in slot[0]. When they
  coincided, both slots held the identical move, silently wasting a
  killer slot in release builds (ASSERT is a no-op there) and tripping
  _NewKillerMove's own IS_SAME_MOVE invariant in DEBUG builds. Fixed by
  skipping the backfill on collision.

- search.c: removed two ASSERT(iBestScore > -NMATE) calls in QSearch
  that encoded an invariant that isn't actually guaranteed -- at an
  early full-width root iteration, or after aspiration-window widening
  following repeated fail-highs, an ancestor frame's iAlpha/iBeta can
  itself already be more extreme than -NMATE with no mate anywhere in
  the line, so a legitimate fail-low placeholder or fail-high score can
  land in mate-magnitude territory purely as a window artifact.
  hash.c's storage path already treats any value <= -NMATE as a sound
  upper bound regardless of origin, so this was a false invariant, not
  a caught bug. Also: minor whitespace cleanup, an added ASSERT
  documenting the futility-margin depth precondition it replaced a
  redundant runtime check for, and PV/leaf-count bookkeeping on the
  mate/draw-at-root leaf paths that was previously skipped.

- util.c: MATEMOVE sentinel moves weren't handled in PV-to-string
  conversion, so a PV ending in a detected mate would either display
  garbage or hit the same-move assert. Added an explicit "<#>" marker.

- test.sh: --egtbpath pointed at a nonexistent /egtb/three;/egtb/four;
  /egtb/five; corrected to /zscratch/egtb, this box's actual EGTB
  location.

- main.c/input.c: --command's initial-command buffer (g_szInitialCommand)
  was a fixed 256-byte array; strncpy(..., SMALL_STRING_LEN_CHAR - 2)
  silently truncated any longer --command string, and -- worse -- when
  the source was long enough not to fit, strncpy doesn't null-terminate
  the destination, so the immediately-following strcat(..., "\r\n") could
  read/write past the buffer. Long move-replay command strings used
  during this session's debugging hit the truncation directly (a ~600
  char move list silently cut off mid-token, desyncing the input queue).
  Changed g_szInitialCommand to a heap allocation sized to the actual
  input length instead of a fixed cap.

- CLAUDE.md: documents the above (this file's own diff is prior
  session's writeup of these same fixes, committed now alongside the
  code).

All exercised together via precommit_check.sh (self-test suite + DEBUG
smoke test against random ecm.ep_ samples) and the sd10/sn5m curated
suite sweep run for the eval.c hand-tuning commit just before this one.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01M9ZDiJhiUajUxh95mTXCFJ

1 files changed, 17 insertions, 9 deletions

diff --git a/src/search.c b/src/search.c
index 61fa428..ab7d122 100755
--- a/src/search.c
+++ b/src/search.c
@@ -358,7 +358,7 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
             if (iScore > iBeta) {
                 StoreLowerBound(mvHash, pos, iScore, uDepth, FALSE);
             }
-            iBestScore = iScore; // TODO: try just beta here
+            iBestScore = iScore;
             goto end;
         }
     }
@@ -516,8 +516,8 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
                     (ctx->uPly >= 2) &&
                     (ctx->sPlyInfo[ctx->uPly - 2].iExtensionAmount <= 0))
                 {
-                    if ((uDepth > THREE_QUARTERS_PLY) &&
-                        (uDepth <= ONE_PLY + THREE_QUARTERS_PLY) &&
+                    ASSERT(uDepth >= THREE_QUARTERS_PLY);
+                    if ((uDepth <= ONE_PLY + THREE_QUARTERS_PLY) &&
                         (iRoughEval + VALUE_KNIGHT <= iAlpha))
                     {
                         uFutilityMargin = (iAlpha - iRoughEval) / 2;
@@ -762,9 +762,9 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
                 (uFutilityMargin) &&
                 (TRUE == fIsLeftoverMove) &&
                 (iExtend <= 0) &&
-                (!IS_ESCAPING_CHECK(mv)) && 
+                (!IS_ESCAPING_CHECK(mv)) &&
                 (!IS_CAPTURE_OR_PROMOTION(mv)) &&
-                (!IS_CHECKING_MOVE(mv)) && 
+                (!IS_CHECKING_MOVE(mv)) &&
                 (!fThreat) &&
                 (ComputeMoveScore(ctx, mv, (x - 1)) < uFutilityMargin))
             {
@@ -843,7 +843,7 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
                     iBestScore = iScore;
                     mvBest = mv;
                     pi->mvBest = mv;
-                    
+
                     if (iScore > iAlpha)
                     {
                         if (iScore >= iBeta)
@@ -919,6 +919,11 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
             ASSERT(IS_CHECKING_MOVE(mvLast));
             ASSERT(InCheck(pos, pos->uToMove));
             iBestScore = MATED_SCORE(ctx->uPly);
+            if ((iAlpha < iBestScore) && (iBestScore < iBeta))
+            {
+                INC(ctx->sCounters.tree.u64LeafCount);
+                UpdatePV(ctx, MATEMOVE);
+            }
             ASSERT(iBestScore <= -NMATE);
             goto end;
         }
@@ -927,6 +932,7 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
             iBestScore = 0;
             if ((iAlpha < iBestScore) && (iBestScore < iBeta))
             {
+                INC(ctx->sCounters.tree.u64LeafCount);
                 UpdatePV(ctx, DRAWMOVE);
             }
             goto end;
@@ -1460,7 +1466,6 @@ QSearch(IN SEARCHER_THREAD_CONTEXT *ctx,
             // If we see a move whose value is zero, the rest of the moves
             // in this ply can be tossed.
             ASSERT(SanityCheckMoves(ctx, x, VERIFY_BEFORE | VERIFY_AFTER));
-            ASSERT(iBestScore > -NMATE);
             goto end;
         }
         mv = ctx->sMoveStack.mvf[x].mv;
@@ -1522,7 +1527,6 @@ QSearch(IN SEARCHER_THREAD_CONTEXT *ctx,
                                                     mv.cTo);
                         }
                         KEEP_TRACK_OF_FIRST_MOVE_FHs(uLegalMoves == 1);
-                        ASSERT(iBestScore > -NMATE);
                         ASSERT(SanityCheckMoves(ctx, x, VERIFY_BEFORE));
                         goto end;
                     }
@@ -1546,7 +1550,6 @@ QSearch(IN SEARCHER_THREAD_CONTEXT *ctx,
             }
         }
     }
-    ASSERT(iBestScore > -NMATE);
     ASSERT(SanityCheckMoves(ctx, x, VERIFY_BEFORE));
 
  end:
@@ -1554,5 +1557,10 @@ QSearch(IN SEARCHER_THREAD_CONTEXT *ctx,
     ASSERT(PositionsAreEquivalent(pos, &pi->sPosition));
     ASSERT(IS_VALID_SCORE(iBestScore) || WE_SHOULD_STOP_SEARCHING);
     DTLeaveNode(ctx, TRUE, iBestScore, pi->mvBest);
+
+    // Note: iBestScore can be +INFINITY or -INFINITY here even in the
+    // absence of a legitimate mate detected if we disallowed stand
+    // pat due to perceived danger early on, when the a..b window had
+    // an extreme bound.  This is "legitimate" but weird.
     return(iBestScore);
 }