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Subject: Re: Crafty's »computer« command?

Author: Bryan Hofmann

Date: 04:07:12 02/04/04

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On February 04, 2004 at 06:16:53, Mike S. wrote:

>In the Crafty doc, I found:
>
>"9.  computer  This command usually  comes  from  xboard/win-
>board,  but  can  be  used  at any time to tell Crafty it is
>playing a computer.  This will prevent some things from hap-
>pening, such as a draw score that varies, as well as adjust-
>ing the book selection code to be more selective in what  it
>plays."
>
>First I seemingly misunderstood that, thinking WinBoard would send that command
>automatically when an engine match is run. This seems not to be the case
>automatically, also not in Arena. (The engine responds to the command when I
>include it in the Crafty.rc file, or typed it in when running Crafty in a DOS
>box.)
>

Winboard will only report playing a computer when it is in ICS mode and the
system is identified as a computer on ICC/FICS.

>What exactly does this command change (I don't quite understand "draw score that
>varies")?

It sets the following;

-accept_draws = 1 (Turns on accepting draws)
-resign = 9 (Set the resign threshold)
-book_selection_width = 1 (set book selection width to 1)
-usage_level = 0 (turns off usage/front end thinking time)
-It also tells crafty yo use the bookc.bin file if it exists.

The "resign 9" will make crafty resign roughly five moves after the score drops
below -9.000.

>
>Does the search and evaluation remain the same (so that results from test suites
>should be the same), with or without computer option?

Yes

>
>IOW., does it only affect book selection and gameplay behaviour so to speak?

Yes it sets it to a width of 1 meaning it will select the top sorted move.

>
>When the differences in book usage are not in effect (i.e. because GUI
>controlled books or predefined opening variants are used): How is Crafty's
>comp-comp performance affected, when the computer option is not turned on? Is an
>estimation possible of the "long run" performance difference caused by that (if
>any)?
>
>I guess, many Crafty (offline) comp-comp games are played without switching that
>option on - just because people don't know about it. I nearly never saw it was
>mentioned anywhere in postings.
>
>Thanks,
>Mike Scheidl



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