Author: Christophe Theron
Date: 11:32:22 04/10/04
Go up one level in this thread
On April 10, 2004 at 06:53:32, José de Jesús García Ruvalcaba wrote:
>On April 09, 2004 at 15:26:34, Christophe Theron wrote:
>
>>On April 09, 2004 at 14:27:48, Sune Fischer wrote:
>>
>>>
>>>>Clearly, nothing beats the ugliness of bitboards.
>>>
>>>This may not be the best example to judge by.
>>>
>>>-S.
>>>> Christophe
>>
>>
>>
>>In the contrary, I think it's fairly typical of bitboard code.
>>
>>Elegance is supposed to be the strong point of bitboards.
>>
>>The only thing I find elegant is the pseudo-great starting idea "64 squares <->
>>64 bits".
>>
>>Passed this point everything becomes unreadable and ugly.
>>
>>I also see it often used to pre-compute attack tables and such, which is in my
>>opinion contrary to one of the most important things I have learned in computer
>>chess: do not compute anything in advance if you are not certain that you will
>>use it. This is not an intrinsic problem of bitboards, it's just that use of
>>bitboards often go along with this misuse of computing resources, is it just by
>>chance?
>>
>>Bitboards are a great tool allowing you to compute very complex things in a
>>blink. The problem is that in a chess program you rarely need to do these
>>complex computations if you know what you are doing, and so you end up with ugly
>>and unreadable code and waste of resources (in particular of L1 and L2 caches).
>>
>>That being said, I do not want to be too harsh: it is probably possible to write
>>a top-level chess program using bitboards, a program that would be not very far
>>behind the programs using more portable approaches like 0x88 and derivatives.
>>
>>Somebody will write one some day.
>>
>>
>>
>> Christophe (setting up a shield for the upcoming flame)
>
>Kaissa and Cray Blitz used bitboards. Of course they might not be top programs
>any longer, but I think it is only fair to compare them against their
>contemporaries, and at their time both were top.
>José.
Given the state-of-the-art at the time (so many efficient techniques were
missing, in particular in their opponents) they could been built on any data
structure.
I don't want to downplay their achievements, but I think that if any comparison
can be done it should be done on current programs.
My opinion is that the basic data structure will not make any dramatic
difference. Bitboards do not bring any significant advantage, and I actually
think that there are other well designed and optimized data structures that are
more efficient. And that will work equally well on any word size target
processor (say from 8 to 128 bits). Because they are more portable, more
readable and as efficient if not more, I consider that they are better than
bitboards.
It's not a "bitboards suck" thread. It's a "guys I don't understand what turns
you on about bitboards" thread.
Christophe
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