Author: Uri Blass
Date: 10:04:07 09/20/04
Go up one level in this thread
On September 20, 2004 at 10:38:31, Robert Hyatt wrote:
>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).
>
>would not work. If I am not in check, I don't use the special move generator
>that generates only legal moves... You would never extend there in Crafty,
>since there are never any positions where there is only one possible
>pseudo-legal move...
I am not sure about the last never
How many possible pseudo legal moves are in the following position
[D]7k/8/8/6p1/5pP1/4pPp1/4P1PN/5B1K w - - 0 1
Uri
>
>
>> 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.
>>
>>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.
>
>No. in_check = 0 says use normal move generator. in_check = 1 says use special
>check-evasion generator so that I don't have to cull all the illegal moves as I
>try to search them.
>
>
>
>>
>>cheers
>> martin
>>
>>
>>>
>>>Can anyone tell something about his or her findings?
>>>
>>>Thanks!
>>>
>>>Renze
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