It's only the piece counters that aren't updated property because the same board is used in the recursion. Placing/undoing a cell position works because it gets the information from the move itself, which btw... doesn't change between and make/unmake.

Your pseudocode snippet is similar to my function. I'm passing the board as one of the parameters and make/unmake the same way.

My make function does:
1. place new piece on the board
2. increment new pieces for current player
3. switch players (opponent is now the current player)

My unmake function does:
1. remove new piece from the board
2. decrement new pieces for current player
3. switch players

However, after a few plies into the search the number of new pieces for each player are way off (eg. 22, -18, etc)

So what could be wrong?

Hi all,

I'm writing a board game and currently implementing the AI using the standard Negamax. This algorithm calls itself recursively.

To speed up things I implemented a makemove/undomove within the function and I don't pass the board object as a parameter to itself. However, due to the nature of Java not passing objects by reference, the changes to the board state when going deeper into the recursion are also reflected into the upper levels.

When I just copy the board state every time, the function works fine because each recursion works on a new copy based on a copy of one level above it. In this case I do have to pass the board state copy as a parameter and this copy copied immediately.

This has serious issues because as I hit a depth of 6 the search slows down considerably. So I'd rather have the move/undo functionality to speed up things.

So my question is: Is it possible in Java, and if yes, how? Or am I restricted to copying the board each and every time with serious performance issues?

Thanks,
C

I've already tried that approach but the function returns just long which I can't use instead of the bits.

Hi all,

Can this code snippet be converted to Java?