Speed up eval/move-gen/SEE; remove EvalLookForDanger, overhaul _EvalKing

SPRT-confirmed improvement (1814 games, st 4.0): candidate nps=1498118
vs head=1378448, avg depth 14.30 vs 13.87, ELO=+24.2+/-16.0,
LOWER95=0.5118, LLR=+3.126 crossing the H1 bound.

Most of the diff is non-semantic speed work across eval.c, generate.c,
movesup.c, see.c, probe.c and friends. Two real semantic changes:
removed EvalLookForDanger and overhauled _EvalKing's king-safety scoring.

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

1 files changed, 91 insertions, 20 deletions

diff --git a/src/see.c b/src/see.c
index dd60537..fa8e8db 100644
--- a/src/see.c
+++ b/src/see.c
@@ -206,7 +206,7 @@ Return value:
 // single-bit bitboard of the actual king square is either that bit or
 // zero, same O(1)-table-lookup shape the knight line already uses, no
 // DISTANCE()==1 branch needed.
-BITBOARD
+BITBOARD FORCEINLINE
 _WhoAttacksSquareBB(IN POSITION *pos,
                      IN COOR cSquare,
                      IN ULONG uSide,
@@ -258,7 +258,7 @@ Return value:
     return bbAttackers;
 }
 
-void CDECL
+void FORCEINLINE
 _GetAttacksBB(IN OUT SEE_LIST *pList,
               IN POSITION *pos,
               IN COOR cSquare,
@@ -319,17 +319,14 @@ Return value:
     // no mailbox load -- entirely replacing what iSeeDelta/pPawn[]
     // used to do at runtime; only the (0-2) actual hits still need a
     // COOR to populate the SEE_LIST.
+    BITBOARD bbPawnHits = g_PawnAttackOriginBB[uSide][cSquare] &
+        pos->bbPawns[uSide];
+    ULONG uPawnBit;
+    while (bbPawnHits)
     {
-        BITBOARD bbPawnHits = g_PawnAttackOriginBB[uSide][cSquare] &
-                               pos->bbPawns[uSide];
-        ULONG uPawnBit;
-
-        while (bbPawnHits)
-        {
-            uPawnBit = FastFirstBit(bbPawnHits) - 1;
-            bbPawnHits &= (bbPawnHits - 1);
-            ADD_ATTACKER(pPawn[uSide], BIT_NUMBER_TO_COOR(uPawnBit), VALUE_PAWN);
-        }
+        uPawnBit = FastFirstBit(bbPawnHits) - 1;
+        bbPawnHits &= (bbPawnHits - 1);
+        ADD_ATTACKER(pPawn[uSide], BIT_NUMBER_TO_COOR(uPawnBit), VALUE_PAWN);
     }
 
     //
@@ -640,7 +637,6 @@ Return value:
     {
         pList->uCount--;
     }
-
 #else // !SEE_HEAPS
 
     //
@@ -698,7 +694,7 @@ Return value:
 
 
 #ifdef SEE_HEAPS
-static PIECE
+static PIECE FORCEINLINE
 _MinLegalPiece(IN POSITION *pos,
                IN ULONG uColor,
                IN SEE_LIST *pList,
@@ -1008,7 +1004,7 @@ Return value:
 }
 
 
-FLAG
+FLAG FORCEINLINE
 SeeFastSign(IN POSITION *pos,
             IN MOVE mv)
 /**
@@ -1084,15 +1080,18 @@ Return value:
 
 
 SCORE
-SEE(IN POSITION *pos,
-    IN MOVE mv)
+_SEEFull(IN POSITION *pos,
+         IN MOVE mv)
 /**
 
 Routine description:
 
-    Given a board and a move on the board, estimate the value of the
-    move by considering the friend/enemy pieces that attack the move's
-    destination square.
+    The real exchange-walk implementation -- see SEE()'s header
+    comment (below) for the cheap early-exit that now sits in front of
+    this, and _SEEFull's own non-static, un-inlined status so
+    testsee.c's TestSEENoDefenderFastPath can call it directly by name
+    for a correctness/speed comparison against SEE(), same convention
+    as _GenerateAllMoves/_GenerateAllMovesBB.
 
 Parameters:
 
@@ -1244,3 +1243,75 @@ Return value:
 #endif
     return(rgiList[0]);
 }
+
+SCORE FORCEINLINE
+SEE(IN POSITION *pos,
+    IN MOVE mv)
+/**
+
+Routine description:
+
+    Given a board and a move on the board, estimate the value of the
+    move by considering the friend/enemy pieces that attack the move's
+    destination square.
+
+    Cheap early exit before paying for any of _SEEFull's work (two
+    GetAttacks calls, sort/heap of both, _AddXRays): if the defending
+    side has NO attacker on mv.cTo -- checked the same x-ray-aware way
+    SeeFastSign already does (mv.cFrom removed from occupancy, so a
+    slider the mover was itself blocking gets counted) -- the exchange
+    can never continue past our own capture, so the true SEE value is
+    exactly PIECE_VALUE(mv.pCaptured) + PIECE_VALUE(mv.pPromoted). This
+    is not an approximation: it is the exact value _SEEFull's own
+    do/while loop would compute on this input (its first
+    _MinLegalPiece call for the defender would find nothing and break
+    immediately, returning rgiList[0] unchanged) -- see
+    TestSEENoDefenderFastPath (testsee.c) for the exact-value
+    correctness gate against _SEEFull, not just a sign check.
+
+    Unlike SeeFastSign (which only ever needs the sign and so can
+    throw the magnitude away), callers of SEE() need the real value --
+    _ScoreAllMoves/_ScoreQSearchMoves* add an ordering bias on top of
+    it and DecodeMoveValueEstimate (searchsup.c) later subtracts that
+    bias back out to recover this exact number for real pruning
+    decisions in _ShouldWeConsiderThisMove. So this early exit has to
+    return the true value, not just resolve a sign and hand back a
+    placeholder -- which is exactly what it does here, no different
+    from what the full exchange walk would have produced.
+
+    Pawn defenders can't be x-ray-revealed by the mover's own
+    departure (a pawn's attack squares are a fixed 2-square delta, not
+    a blockable ray), so that check alone uses the raw board, matching
+    SeeFastSign's identical reasoning.
+
+Parameters:
+
+    POSITION *pos,
+    MOVE mv
+
+Return value:
+
+    SCORE : the estimate of the move's score
+
+**/
+{
+    ULONG uDefender = FLIP(GET_COLOR(mv.pMoved));
+    BITBOARD bbOccupiedWithoutMover;
+
+    if (g_PawnAttackOriginBB[uDefender][mv.cTo] & pos->bbPawns[uDefender])
+    {
+        return _SEEFull(pos, mv);
+    }
+    bbOccupiedWithoutMover = pos->bbOccupied & ~COOR_TO_BB(mv.cFrom);
+    if (_WhoAttacksSquareBB(pos, mv.cTo, uDefender, bbOccupiedWithoutMover))
+    {
+        return _SEEFull(pos, mv);
+    }
+
+    //
+    // No defender at all -- the exchange can't continue past our own
+    // move, so the result is exactly the material gained (captured +
+    // promoted).
+    //
+    return (SCORE)(PIECE_VALUE(mv.pCaptured) + PIECE_VALUE(mv.pPromoted));
+}