Author: Uri Blass
Date: 05:19:22 09/20/04
Go up one level in this thread
On September 20, 2004 at 07:17:17, martin fierz wrote:
>On September 20, 2004 at 06:11:49, Renze Steenhuisen wrote:
>
>>On September 20, 2004 at 06:00:21, martin fierz wrote:
>>
>>>On September 20, 2004 at 05:28:54, Renze Steenhuisen wrote:
>>>
>>>>Hi all,
>>>>
>>>>I have to confess that this is a very said thing, but I have to ask...
>>>>
>>>>My moveGen() generates pseudo-legal moves, in a similar way as is done in
>>>>Crafty. I want to add the single-reply extension (of course), but I find it hard
>>>>to grasp how to do this efficiently (because I might need to generate more moves
>>>>than needed, right?)
>>>>
>>>>Or someone could please explain in words what is done in Crafty:
>>>>
>>>> if (tree->in_check[ply] && tree->last[ply]-tree->last[ply-1] == 1) {
>>>> tree->one_reply_extensions_done++;
>>>> extended+=onerep_depth;
>>>> }
>>>>
>>>>What is this "tree->last[]" thing doing exactly?
>>>>
>>>>Thanks!
>>>>
>>>> Renze
>>>
>>>i never studied the crafty code very thoroughly so i might be wrong. i think
>>>tree->last[ply] is the move stack pointer, which means that if the condition
>>>tree->last[ply] - tree->last[ply-1] == 1
>>>is true, there is exactly one move at ply. so basically this doesn't answer your
>>>question how to do it efficiently - it's just part of crafty's housekeeping that
>>>bob is using here. the (efficient) generation of the check evasions is being
>>>done somewhere else (and i have no idea where!)
>>
>>Aha! Check! of course, that's it. (STUPID ME)
>>
>>So Crafty is only doing one_rep extension when in check!
>>
>>But, isn't the idea of the extension to extend all situations where there is
>>merely ONE LEGAL REPLY?
>
>i don't think so. in fact, it would be extremely easy to add such an extension
>(just remove the 'tree->in_check[ply]' part in crafty). but i would guess that
>99.999% of all situations where there is only one move are checks. i can't
>remember seeing any position ever in my games where there was only one reply
>without checks. perhaps in some kind of study it might happen, but not in normal
>games.
It can happen in normal games if the opponent refuse to resign in some lost
position when he has only king but of course extending these positions is not a
good idea.
Uri
>
>so the whole point of bob's code is that it runs 0.01% faster if he first checks
>for in_check and only then checks the (a-b == 1) thing, because he saves the
>a-b. at least that's what i assume when looking at it.
>
>cheers
> martin
>
>
>>
>>Can anyone tell something about his or her findings?
>>
>>Thanks!
>>
>>Renze
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