Author: Sune Fischer
Date: 06:36:20 01/28/02
Go up one level in this thread
On January 28, 2002 at 09:26:15, Vincent Diepeveen wrote:
>On January 28, 2002 at 08:36:15, Sune Fischer wrote:
>
>>Hi,
>
>>I'm in the process of rewriting my entire movegen, now I'm going to need
>>bitboards I've decided, but it seems there are different approaches.
>
>i would not have taken that decision but if you must chose what to use,
>my tip is to start with normal bitboards, changing them to rotated
>later can always be done, but try to keep the RAM used for it low!
>
>modifying normal bitboards to rotated bitboards is something you can
>do later.
That's where I'm at now, at "later". I have had bitboards from day 1, but just
generated very inefficient.
>Reversed bitboards, we have seen a posting or 2 about it, but till there
>is an implementation for that actually works, it is going to be interesting
>to take a look at it without any serious plans.
Bah, you guys are no fun, live a little, risk it all!;)
If it works it should be faster, I'll think it through and if I can't find any
flaws I'll give it a try.
>Only the diagonals you need to take a look at at the design what is faster
>for them. if that problem isn't solved in reversed bitboards, then obviously
>rotated are going to be easier for you to take a look at.
K, I will.
>It seems there are however many methods at the K7 + intel processors to
>use with rotated bitboards. In isichess it seems smaller tables are
>getting used than in crafty for this.
>
>Others report they do it even different, but their speedresults are
>not impressive.
>
>>I found this link (it was actually dead, but google had it cached so I put it up
>>for a short while)
>>http://www.fys.ku.dk/~fischer/Temp/New%20Technology.htm
>>
>>It is about reversed bitboards, the author claims it is faster than rotated:
>>
>>"When taking account of memory latencies, calculating the piece attacks using
>>the forward and reverse bitboards can be done significantly faster due to total
>>independence on lookup tables and complex calculations. There are a few slight
>>snags with the diagonal calculations, but they are minor."
>>
>>
>>His description ("significantly faster") entrigues me (hehe) but I can't find
>>anything else on reversed bitboards and I've never heard of them before.
>>
>>What's the catch, is there something he is not telling?
>>
>>-S.
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