hoover_chess_utils::pgn_reader::Attacks_Portable Class Reference

Portable implementations for attacks. More...

#include <bitboard-attacks-portable.h>

Static Public Member Functions
static SquareSet	getPawnAttackMask (Square sq, Color pawnColor) noexcept
static SquareSet	getPawnAttackerMask (Square sq, Color pawnColor) noexcept
template<Color pawnColor, bool captureToRight>
static constexpr SquareSet	getPawnAttackersMask (SquareSet capturable) noexcept
static SquareSet	getKnightAttackMask (Square sq) noexcept
static SquareSet	getKingAttackMask (Square sq) noexcept
static SquareSet	getBishopAttackMask (Square sq, SquareSet occupancyMask) noexcept
	See Attacks::getBishopAttackMask() for usage documentation.
static SquareSet	getRookAttackMask (Square sq, SquareSet occupancyMask) noexcept
	See Attacks::getRookAttackMask() for usage documentation.
static SquareSet	getHorizRookAttackMask (Square sq, SquareSet occupancyMask) noexcept
	Returns horizontal rook attack mask.

Static Private Member Functions
static SquareSet	getSliderAttackMaskHyperbola (SquareSet pieceBit, SquareSet occupancyMask, SquareSet rayMaskEx) noexcept
	Calculate vertical, diagonal, or antidiagonal attack mask using the Hyperbola quintessence algorithm.

Detailed Description

Portable implementations for attacks.

Member Function Documentation

getBishopAttackMask()

static SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getBishopAttackMask ( Square  sq, SquareSet  occupancyMask  )

inlinestaticnoexcept

See Attacks::getBishopAttackMask() for usage documentation.

Parameters

[in]	sq	Bishop square
[in]	occupancyMask	Set of occupied squares

Returns

Set of attacked squares

getSliderAttackMaskHyperbola() is used to implement this function.

getHorizRookAttackMask()

static SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getHorizRookAttackMask ( Square  sq, SquareSet  occupancyMask  )

inlinestaticnoexcept

Returns horizontal rook attack mask.

Parameters

[in]	sq	Rook square
[in]	occupancyMask	Set of occupied squares

Returns

Set of horizontally attacked squares

getKingAttackMask()

static SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getKingAttackMask ( Square  sq )

inlinestaticnoexcept

getKnightAttackMask()

static SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getKnightAttackMask ( Square  sq )

inlinestaticnoexcept

getPawnAttackerMask()

static SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getPawnAttackerMask ( Square  sq, Color  pawnColor  )

inlinestaticnoexcept

getPawnAttackersMask()

template<Color pawnColor, bool captureToRight>

static constexpr SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getPawnAttackersMask ( SquareSet  capturable )

inlinestaticconstexprnoexcept

getPawnAttackMask()

static SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getPawnAttackMask ( Square  sq, Color  pawnColor  )

inlinestaticnoexcept

getRookAttackMask()

static SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getRookAttackMask ( Square  sq, SquareSet  occupancyMask  )

inlinestaticnoexcept

See Attacks::getRookAttackMask() for usage documentation.

Parameters

[in]	sq	Rook square
[in]	occupancyMask	Set of occupied squares

Returns

Set of attacked squares

getSliderAttackMaskHyperbola() is used to implement the vertical attack mask resolution.

The horizontal attack mask is resolved as follows:

1. Determine row and column of the attacking piece sq
2. Determine shift for translating the row to the first rank (row * 8U)
3. Shift the piece rank to first rank
4. Use a precomputed table mapping the first rank occupancy and piece column to attack squares
5. Shift the attack squares back to piece row

getSliderAttackMaskHyperbola()

static SquareSet hoover_chess_utils::pgn_reader::Attacks_Portable::getSliderAttackMaskHyperbola ( SquareSet  pieceBit, SquareSet  occupancyMask, SquareSet  rayMaskEx  )

inlinestaticprivatenoexcept

Calculate vertical, diagonal, or antidiagonal attack mask using the Hyperbola quintessence algorithm.

Parameters

[in]	pieceBit	Square set containing only the attacking piece
[in]	occupancyMask	Occupied squares
[in]	rayMaskEx	Forward/backward attack ray excluding the attacking piece. For example, the file of the rook not including the rook.

Returns

Attacked squares

Illustration

Input	Return
o o o o o o o o o o o o o o R o o o o o o o o o o o	x x x x x
o = occupied square shaded squares = rayMaskEx R = attacker	Squares marked with x = return

Design

The implementation uses a variation of the "o^(o-2r)" trick. First, the occupancy mask is AND'd with the ray mask.

		o
		o
		o

Then, two copies are taken: one as is (left side) and one mirrored vertically (right side):

o o o

o o o

The attacking piece is subtracted from the boards. Note that the attacking piece bit is also flipped vertically in the right-side board.

o o o o o o o o o o o o o o o o o o

o o o o o o o o o o o o o o o o o o o o o o o o o o

The right-side board is flipped vertically again.

o o o o o o o o o o o o o o o o o o

o o o o o o o o o o o o o o o o o o o o o o o o o o

The left-side and right-side boards are then XOR'd together.

o	o	x
o	o	x	o	o	o	o	o
o	o	x	o	o	o	o	o
o	o	x	o	o	o	o	o
o	o	x

and the result is AND'd with the ray mask. This gives the final result.

The XOR operation isolates the bits that change in the subtraction operation. This is the reason why this algorithm works.

See also

https://www.chessprogramming.org/Hyperbola_Quintessence

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The documentation for this class was generated from the following file:

• pgn-reader/src/bitboard-attacks-portable.h