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Subject: Re: Bitboard by any simple engine?

Author: Anthony Cozzie

Date: 16:52:40 05/30/04

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On May 29, 2004 at 16:09:22, Sune Fischer wrote:

>On May 29, 2004 at 14:41:28, Anthony Cozzie wrote:
>
>>On May 29, 2004 at 14:26:55, Russell Reagan wrote:
>>
>>>On May 29, 2004 at 04:24:18, Tony Werten wrote:
>>>
>>>>Yes, you would have to hop to nextsquare to see how it would go from there. Now
>>>>you only have to look what square we are talking about, and if !nil, you will
>>>>always know that the nextsquare will be given at *sq++
>>>>
>>>>So you basicly made "nextsq" and "location of nextsq" independant of each other,
>>>>thereby making it independant of board representation and making it more
>>>>efficient since you will be traveling through the array in a row, rather than
>>>>randomly accesed.
>>>
>>>Would this be any faster than a traditional array based move generator? As far
>>>as I can tell, the array based movegen will iterate over an array, while the
>>>move table approach loops over a linked list (effectively). Looping over an
>>>array will almost always be at least as fast as looping through a linked list,
>>>right? Plus the move table approach uses more memory to accomplish the same
>>>thing. You may get some other advantages from a move table approach, but with
>>>regard to speed, the move table approach doesn't seem like it would be the
>>>fastest.
>>
>>The magic of Vincent's generator is that there are almost no branches and
>>relatively little memory.  The two biggest wastes of time in a modern deeply
>>pipelined superscalar processor are branch mispredictions and cache misses.
>>
>>anthony
>
>I really don't understand all the hype about a generator.
>I just had a look at a profile, mine spends something like 5% generating moves.
>That's hardly worth even looking at to optimize.
>
>It might be due to its incremental design that it's so fast though ;)
>
>Sorting the moves however, now that takes time.
>
>-S.

Greatest thing since sliced bread? no.  Elegant code? yes.

Also, a fast move generator is useful for other scans, like incremental attack
table update.

anthony



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