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Subject: Re: Parallel algorithms in chess programming

Author: Josť Carlos

Date: 06:04:42 04/18/01

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On April 18, 2001 at 05:25:52, Vincent Diepeveen wrote:

>On April 17, 2001 at 16:07:35, Josť Carlos wrote:
>
>>On April 17, 2001 at 14:51:45, Gian-Carlo Pascutto wrote:
>>
>>>On April 17, 2001 at 13:30:22, Vincent Diepeveen wrote:
>>>
>>>>> Are you sure you spend most of your time in eval? My problem is inCheck()
>>>>>since ever. That's where my prog spends most of the time.
>>>>>  The good thing is that, everytime I want to improve the speed of my
>>>>>program, I know exactly where to focus on :)
>>>>>  I suggest you to profile your program to know exactly where the time is
>>>>>spend, although probably you've already done this.
>>>>>
>>>>>  Josť C.
>>>>
>>>>How can this eat system time anyway?
>>>
>>>If you dont have any attack information available incheck can be
>>>costly. In Sjeng it topped the running profile a long time, though only
>>>with 15%-20% of the total time or so.
>>>
>>>I speeded my incheck/legal_move up greatly by looking at the move last
>>>played and figuring out if it could possibly have put the king in check.
>>
>>  Exactly. That's what I'm doing right now. But actually my makemove() function
>>is about 5000 lines !!! And I still haven't remove half the inCheck() calls !!
>>  This is driving me mad, since there're a lot of rare cases that you must take
>>into account. Really hard, but I hope it's worth the effort.
>
>what do you do in makemove?
>
>If you do next:
>
> if( possiblecheck[piece][fromfield][kingfield]
>  && scanbetween(piece,fromfield,kingfield) )

  I see. You have all that information stored in a table, so a lookup is enough.
But anyway, suppose you're already in check. Now you capture a pawn en passant.
Are you still in check after that?
  You have to check if the captured pawn was checking your king. Depending on
whether that's true or false, you much check if both pawns disappearing open a
line for an enemy sliding piece towards your king. If all of that if false, you
still need to check if there was another piece cheking your king (it could be a
double check), etc...
  I don't see how you know it so easily.

  Josť C.

>i do not see how figuring out whether such a move is a check can cost
>more as say 1% system time even in a program getting half a million
>nodes a second at a PII450.
>
>Best regards,
>Vincent
>
>>  Josť C.
>>
>>>You can apply a lot of tricks to make this very fast.
>>>
>>>Now it is way down on the profile (>3% or so), and my program became about
>>>6% faster. Now need to find a way to get SEE attack info quicker :)
>>>
>>>--
>>>GCP



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