• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
patishi

Checking for offboard squares with bitboards (vs padded array)

8 posts in this topic

I am currently starting to work on a chess engine.

With padded array it is easy to check for offboard squares,  but what if I want to use bitboards to represent the board, how should I make this validation?      should I keep a padded array (along with the bitboards)  for those checks or there are maybe another more effiecient / bitboard oriented solutions ?

 

Thx

Edited by patishi
0

Share this post


Link to post
Share on other sites

Ah, to be honest, I had to look up what you wanted:

http://www.cis.uab.edu/hyatt/boardrep.html

Seems to answer a lot of questions related to board layouts.

 

But honestly, I think at this point in computing, it's over optimizing to even worry about whether to pad your chessboard with offboard squares or not.  A simple function or macro that is something like IsValid(x,y) will abstract it away, and you can just use whatever is most straightforward and most expedient for you at the moment.  Unless of course you want to rival Deep Blue or whatever the reigning king is and want to get super fast chess computation.

0

Share this post


Link to post
Share on other sites

I have written chess engines before, and I don't think it's over-optimizing. Keeping your code board-representation-agnostic using macros is not very realistic, because many of the algorithms you will use (Static Exchange Evaluation, repetition detection, what terms to use in the evaluation function...) and other data descriptions (moves, transposition-table entries...) will be heavily affected by the choice of representation. If you want to change your board representation after you have written an engine, you will be better off starting from scratch.

 

Bitboards are great, but they require a shift in how you think about a lot of things. In particular, being outside the board is not a very meaningful concept. For the most part, you don't handle squares one at a time when using bitboards: The basic data structure is a subset of the squares, and operations like moving North move all of them. Some of the bits that were set before moving North will seem to have disappeared, and that's about all there is to it.

 

 typedef unsigned long long u64;
  
  u64 North(u64 x) {
    return x << 8;
  }

 

If you have a specific example of code where you feel you need to check if a square is outside the board, post some details about what you are doing and I'll try to help you express it with bitboards.

1

Share this post


Link to post
Share on other sites
Thx for the responses.
Alvaro, I read your comment but i'm having a little hard time to understand it completely.

Let's say the white queen is on A8,now it can't move north anymore cause there is no more board left. I need to make some kind of validation..
If I try translate ir to bitboard terms, A8 is the 57th bit, and if I do <<8 I will get strange results.
what am missing here??

Please bare with me , like you said..thinking OUTSIDE of the board requires a change in how you look at things.

Thx
0

Share this post


Link to post
Share on other sites

Let's say the white queen is on A8,now it can't move north anymore cause there is no more board left. I need to make some kind of validation..
If I try translate ir to bitboard terms, A8 is the 57th bit, and if I do <<8 I will get strange results.
what am missing here??


No strange results: You'll get 0, which means the queen is nowhere on the board.

More importantly, why are you moving North from A8? Are you trying to generate moves? The way you would normally generate moves using bitboards doesn't require this operation at all.
0

Share this post


Link to post
Share on other sites
I was planning to loop through each piece in every direction and check for available moves until i hit the edge of the board.. but i guess that i can simply get the available squares by means of bit operations on the relevant bitboards?
0

Share this post


Link to post
Share on other sites
Move generation with bitboards is normally not done that way. Let's concentrate on sliding pieces (all the others are much easier). You pick one piece at a time, you compute a bitboard of all the places where it could go and then generate moves to go to each of those places. Why would you want to do it this way? Because the majority of the time in the search tree is spent in the quiescence search, where you mostly need to generate only captures. If you have a bitboard of the places where the piece could go, you can bitwise-AND it with the enemy pieces and get your captures, without having wasted any time on non-captures.

How do you compute the places where the piece might go? There are several ways to do it. The one I have implemented is called magic bitboards.
0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0