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Subject: Re: detecting and evaluating pins

Author: Robert Hyatt

Date: 08:14:00 02/24/04

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On February 24, 2004 at 09:27:26, martin fierz wrote:

>On February 23, 2004 at 11:14:28, Robert Hyatt wrote:
>
>>On February 23, 2004 at 07:02:59, martin fierz wrote:
>>
>>>aloha,
>>>
>>>i have a question about pins. pins are a rather important feature in chess; some
>>>of them are not so bad, some are deadly. i just happened to chat briefly with
>>>anthony cozzie on ICC, and he said he didn't do any pin detection. i detect
>>>pins, but i don't evaluate whether a pin is not so bad or deadly. my questions
>>>are:
>>>-> are you detecting pins in your program?
>>>-> if yes, do you try to distinguish between different pins?
>>
>>No and No.  I don't do it as I have not found it very important.  IE with the
>>depth I hit today, if a pin is important, the search can go deeply enough to
>>discover this without much trouble.  20 years ago I was definitely evaluating
>>pins, as hitting 5-6-7 plies is not deep enough to see the consequences of a
>>pin, whereas todays 12-16 plies in longer games is more than enough in most
>>cases.
>
>interesting - and a possible explanation why i believe i need them. muse
>searches something like 1-2 plies less than crafty on equal hardware (meaning
>single-processor hardware of course...), and i play blitz matches. so i'm
>getting something in between of your 5-7 and 12-16 plies; meaning that i am
>closer to needing pin detection than you are :-)
>
>cheers
> martin

You are also in the danger-zone for null-move R=2 and R=3 as well, at those
depths.  If you look at the comments in main.c in Crafty, you will see how many
times I tried R=2 from 1994 to date, and how many times it failed, until the
depth reached a point where null-move didn't hide too many tactics...

Depth is definitely part of the formula, and the deeper we go, the more things
change in unexpected ways...


>
>>There are exceptions, but the question has to be "is the cost of doing this
>>offset by the playing strength increase?"  I believe that at least for my
>>program, the answer is "no".
>>
>>YMMV of course.
>>
>>>
>>>cheers
>>>  martin



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