Pinned Pieces With Bitboards

[tcusr]

While reading an article on CPW regarding checks and pinned pieces: https://www.chessprogramming.org/Checks ... Bitboards)
I didn't fully understand this function:

Code: Select all

 pinned = 0;
pinner = xrayRookAttacks(occupiedBB, ownPieces, squareOfKing) & opRQ;
while ( pinner ) {
   int sq  = bitScanForward(pinner);
   pinned |= obstructed(sq, squareOfKing) & ownPieces;
   pinner &= pinner - 1;
}
pinner = xrayBishopAttacks(occupiedBB, ownPieces, squareOfKing) & opBQ;
while ( pinner ) {
   int sq  = bitScanForward(pinner);
   pinned |= obstructed(sq, squareOfKing) & ownPieces;
   pinner &= pinner - 1;
}

My question is what the function obstructed() does. Moreover, I would like to know whether opRQ refers to the rooks and queens. And whether opBQ refers to the bishops and queens.

Thanks.

yes opRQ contains both opposite rooks and queens, it's useful because the queen is just a rook + bishop, so you can save computation.
obstructed returns the bits between sq (the possible pinner) and squareOfKing

[StackFish5]

While reading an article on CPW regarding checks and pinned pieces: https://www.chessprogramming.org/Checks ... Bitboards)
I didn't fully understand this function:

Code: Select all

 pinned = 0;
pinner = xrayRookAttacks(occupiedBB, ownPieces, squareOfKing) & opRQ;
while ( pinner ) {
   int sq  = bitScanForward(pinner);
   pinned |= obstructed(sq, squareOfKing) & ownPieces;
   pinner &= pinner - 1;
}
pinner = xrayBishopAttacks(occupiedBB, ownPieces, squareOfKing) & opBQ;
while ( pinner ) {
   int sq  = bitScanForward(pinner);
   pinned |= obstructed(sq, squareOfKing) & ownPieces;
   pinner &= pinner - 1;
}

My question is what the function obstructed() does. Moreover, I would like to know whether opRQ refers to the rooks and queens. And whether opBQ refers to the bishops and queens.

Thanks.

yes opRQ contains both opposite rooks and queens, it's useful because the queen is just a rook + bishop, so you can save computation.
obstructed returns the bits between sq (the possible pinner) and squareOfKing

So the obstructed function is the same function as the one under Pure Calculation from https://www.chessprogramming.org/Square ... tackBySide ?

[tcusr]

yes

[StackFish5]

Thank you to everyone that responded!