Author: Vincent Diepeveen
Date: 09:25:28 01/28/02
Go up one level in this thread
On January 28, 2002 at 09:36:20, Sune Fischer wrote:
>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!;)
In fact there has been more experimented here than you thought :)
But the hard facts are that if you would go for every thought of a
18 year old kid who can't program, that you are busy for another 1000
years checking out all the crap.
Note that in this case it is not entire crap. The idea to fiddle with a
bunch of MMX instructions in order to get something done in a bitboard
concept is pretty interesting. Nevertheless it depends heavily on your
evaluation.
IMHO bitboards are good for pawn structure but they suck further. Note
there are another zillion solutions to pawn structures and 32 bits
bitboards which are fast too.
>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.
the idea of rotated bitboards is pretty simple, it basically solves
the problem of the sliding pieces. So when someone mentions reversed
bitboards i don't care for knights for example, but *only* for
bishops, rooks.
I have missed the tricks how to do that with other solutions than rotated
bitboards in an efficient way.
>
>>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.
This page took 0.01 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.