board.GetLegalMoves includes illegal moves when in check

[Apoptosis847639]

When your king is in check board.GetLegalMoves includes moves that does not prevent the check so my bot will make an illegal move. I have no idea if this is intentional so if it is I will close the issue.

[mcthouacbb]

Are you sure? I've had no such problem. Do you have a way to reproduce this behavior?

[Apoptosis847639]

So my bot tried to play dxe4 which would have been legal if black was not in check so maybe its my bot or board.GetLegalMoves

[pmwmedia]

So my bot tried to play dxe4 which would have been legal if black was not in check so maybe its my bot or board.GetLegalMoves

I can confirm that board.GetLegalMoves() is broken. The method returns illegal moves when the king is in check.

[SebLague]

It is unlikely that this is a bug in the GetLegalMoves method since the board UI was able to detect that the move is illegal.

The most common cause for a bot making illegal moves is if there's a mistake in the order that moves are made/undone on the board (for example forgetting to undo a move when exiting early from search due to checkmate/etc).

If you're struggling to track down the bug, I suggest asking in the discord if anyone's willing to lend a second pair of eyes. (link in readme)

[Firestorm-253]

Pls share the relevant code snippets for help. I can confirm that the following FEN didn't produce any illegal moves for me.

[Firestorm-253]

I recommend to do a simple check in the main 'Think()' Method before returning the chosen Move: If (!board.GetLegalMoves().Contains(chosenMove)) { throw new Exception("ERROR: I messed smt up") }

otherwise what you can try to debug the error yourself is create a node class including infos like the FEN, played moves so far, eval, depth, subNodes, etc. and then track it down from where this d5e5 comes from.