Variables for Relational Operators?

Programming Questions

asimes

Variables for Relational Operators?

in Programming Questions • 1 years ago

Is it possible to use a variable to flip between "<" and ">"?

I'm making a chess environment and pieces are stored as positive numbers for white and negative for black (white pawn is a "1" and black pawn is a "-1" for example). I have a long series of conditional statements that make a list of possible moves for an AI to use and it set up at the moment for black. If I could just flip all the ">" to "<" in the statements during white's turn it would still correctly make a list of possible moves for white as well.

Replies(4)

asimes

Re: Variables for Relational Operators?

1 years ago

Opps, I realized I can just multiply the pieces by -1 during white's turn. I would still like to know if this is possible though

PhiLho

Re: Variables for Relational Operators?

1 years ago

Not, it is not possible.
And a better data management could solve the problem more elegantly... Eg. using a variable indicating the camp a piece belongs to, instead of using the old fashioned sign trick (I used that when I coded in C...).
When I see " a long series of conditional statements", I see a "code smell", too. Sometime, using arrays or other data structures avoids such code writing.

jbum

Re: Variables for Relational Operators?

1 years ago

I like your solution, actually.

Negating the scoring function for even plies (e.g. white's turn) is the usual way to handle recursive minimax search in chess programs. The idea is you want to use exactly the same logic for white and black, and just reverse the results for the opponent's moves. (I've been doing chess software on/off since the early 90s).

I implemented a minimax tree for my version of Reversi (Othello) that I implemented in Processing, which you'll find here:

http://openprocessing.org/visuals/?visualID=1274

Buried in that code is this line:

// flip score if we're white

if ((cgrid.turnIdx & 1) != 0)

score = -score;

Look familiar?

asimes

Re: Variables for Relational Operators?

1 years ago

@phi.lho, The conditional statements are necessary to limit possible piece movements to fit with the rules of chess. The pieces are not stored, the board is.

int board[] = new int[64]; // 64 because there are 64 squares. Negative elements are black and positive are white

So if I run a for loop through the board's values and one of them is equal to -1 I know it is a black pawn. If I flip the value it is a white pawn. After I know what kind of piece I'm dealing with I can give it rules.

@jbum, This is my second chess environment in Processing. The first one was too slow to be able to have an AI plan moves beyond a turn into the future (unless I expect people to wait 30 seconds every turn). I can tell that this version will be much faster but I don't know how fast.

You said you have been making chess software for some time now, have you ever made one in Processing? I know there are chess programs that can quickly look several moves into the future (within a few seconds), is this because the environment is that efficient or should I look to a faster code language to do this?

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