optimize EvadesCheck()

stephenjlovell · stephenjlovell · commit 320ac5b72cc4 · 2017-02-07T19:38:56.000-05:00
diff --git a/move_validation.go b/move_validation.go
@@ -19,11 +19,7 @@ func (brd *Board) LegalMove(m Move, inCheck bool) bool {
 // Moves generated while in check should already be legal, since we determine this
 // as a side-effect of generating evasions.
 func (brd *Board) AvoidsCheck(m Move, inCheck bool) bool {
-	// return inCheck || brd.PseudolegalAvoidsCheck(m)
-	if inCheck && !brd.PseudolegalAvoidsCheck(m) {
-		fmt.Println("{!}")
-	}
-	return brd.PseudolegalAvoidsCheck(m)
+	return inCheck || brd.PseudolegalAvoidsCheck(m)
 }
 
 func (brd *Board) PseudolegalAvoidsCheck(m Move) bool {
@@ -36,6 +32,8 @@ func (brd *Board) PseudolegalAvoidsCheck(m Move) bool {
 		} else {
 			return pinnedCanMove(brd, m.From(), m.To(), brd.c, brd.Enemy())
 		}
+	case KNIGHT: // Knights can never move when pinned.
+		return isPinned(brd, brd.AllOccupied(), m.From(), brd.c, brd.Enemy()) == BB(ANY_SQUARE_MASK)
 	case KING:
 		return !isAttackedBy(brd, brd.AllOccupied(), m.To(), brd.Enemy(), brd.c)
 	default:
@@ -50,40 +48,38 @@ func (brd *Board) EvadesCheck(m Move) bool {
 
 	if piece == KING {
 		return !isAttackedBy(brd, occAfterMove(brd.AllOccupied(), from, to), to, e, c)
-	} else {
-		occ := brd.AllOccupied()
-		kingSq := brd.KingSq(c)
-		threats := colorAttackMap(brd, occ, kingSq, e, c)
-
-		// TODO: EvadesCheck() called from non-check position in rare cases. Examples:
-		// 5r1k/1b3p1p/pp3p1q/3n4/1P2R3/P2B1PP1/7P/6K1 w - - 0 1
-		// 8/PPKR4/1Bn4P/3P3R/8/2p4r/pp4p1/r6k w - - 5 2  (r h3h5 x r)...?
+	}
+	occ := brd.AllOccupied()
+	kingSq := brd.KingSq(c)
+	threats := colorAttackMap(brd, occ, kingSq, e, c)
 
-		if threats == 0 {
-			fmt.Println("info string EvadesCheck() called from non-check position!")
-			brd.Print()
-			m.Print()
-			return brd.PseudolegalAvoidsCheck(m)
-		}
+	// TODO: EvadesCheck() called from non-check position in rare cases. Examples:
+	// 5r1k/1b3p1p/pp3p1q/3n4/1P2R3/P2B1PP1/7P/6K1 w - - 0 1
+	// 8/PPKR4/1Bn4P/3P3R/8/2p4r/pp4p1/r6k w - - 5 2  (r h3h5 x r)...?
 
-		if popCount(threats) > 1 {
-			return false // only king moves can escape from double check.
-		}
-		if (threats|intervening[furthestForward(e, threats)][kingSq])&sqMaskOn[to] == 0 {
-			return false // the moving piece must kill or block the attacking piece.
+	if threats == 0 {
+		fmt.Println("info string EvadesCheck() called from non-check position!")
+		brd.Print()
+		m.Print()
+		fmt.Printf("King sq: %d\n", kingSq)
+		fmt.Println(brd.InCheck())
+		if !isBoardConsistent(brd) {
+			panic("inconsistent board state")
 		}
-		if !pinnedCanMove(brd, from, to, c, e) {
-			return false // the moving piece can't be pinned to the king.
-		}
-		if brd.enpTarget != SQ_INVALID && piece == PAWN && m.CapturedPiece() == PAWN && // En-passant
-			brd.TypeAt(to) == EMPTY {
-			occ = occAfterMove(occ, from, to) & sqMaskOff[brd.enpTarget]
+		return brd.PseudolegalAvoidsCheck(m)
+	}
 
-			return colorAttackMap(brd, occ, kingSq, e, c) == 0
-			// return attacks_after_move(brd, occ, occ&brd.occupied[e], king_sq, e, c) == 0
-		}
+	if popCount(threats) > 1 {
+		return false // only king moves can escape from double check.
+	}
+	if (threats|intervening[furthestForward(e, threats)][kingSq])&sqMaskOn[to] == 0 {
+		return false // the moving piece must kill or block the attacking piece.
+	}
+	if brd.enpTarget != SQ_INVALID && piece == PAWN && m.CapturedPiece() == PAWN && // En-passant
+		brd.TypeAt(to) == EMPTY {
+		return isPinned(brd, occ&sqMaskOff[brd.enpTarget], from, c, e)&sqMaskOn[to] > 0
 	}
-	return true
+	return pinnedCanMove(brd, from, to, c, e) // the moving piece can't be pinned to the king.
 }
 
 // Determines if a move is otherwise legal for brd, without considering king safety.
@@ -95,10 +91,6 @@ func (brd *Board) ValidMove(m Move, inCheck bool) bool {
 	piece, from, to, capturedPiece := m.Piece(), m.From(), m.To(), m.CapturedPiece()
 	// Check that the piece is of the correct type and color.
 	if brd.TypeAt(from) != piece || brd.pieces[c][piece]&sqMaskOn[from] == 0 {
-		// if brd.TypeAt(from) == piece {
-		// 	brd.Print()
-		// 	m.Print()
-		// }
 		// fmt.Printf("No piece of this type available at from square!{%s}", m.ToString())
 		return false
 	}
