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Subject: Re: Crafty and fastest Cray: question to Bob

Author: Robert Hyatt

Date: 06:23:00 12/01/97

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On December 01, 1997 at 02:10:57, Jouni Uski wrote:

>1) How fast would Crafty be in the fastest possible Cray available today
>and how strong expect you it then play in comparison to Pcs and
>Deep Blue?
>2) Is there any plans to use Cray to run Crafty in future??
>
>Thanks in advance Jouni

Hi Jouni...

(1) I really don't know.  The fastest machine around right now is a
500mhz (2 nanosecond cycle time) T90, with 32 processors.  With some
work, crafty should probably be able to search around 500K nodes per
second per processor, which would hit around 16M nodes per second
overall.  Factoring in the typical (for Cray Blitz) 75% efficiency
that we got, this would be an effective speed of 12M nodes per second.
Really nowhere near DB's speed, although it is not nearly so far away
as Crafty (or any other program) on a micro, even a very fast alpha.

I don't know how strong it would be.  This is about 150X faster than
Crafty on a P6/200.  Figuring a conservative factor of 3X per ply (it
is closer to 2-2.5) suggests this would be worth 4-5 plies of additional
search depth.  Probably more like 7-8 as a best guess.

(2) not at present.  One of the reasons I started to work on a PC-based
chess engine was machine availability.  Getting time on a Cray is
difficult
to impossible, when the machine sells for roughly 60 million dollars.
So
testing and tuning is really impossible.  Thinking back, it is
absolutely
amazing how lucky we were over the years to win as many computer chess
events as we won, because (except for very rare exceptions) the only
games
we ever played on a Cray were the games in the tournament we competed
in.
*not* a good way to develop a consistent program.

You will probably see a parallel crafty before too much longer, one that
will particularly scream on a parallel alpha.  And this code would
probably
port to the Cray and run like the blazes, but getting machine time on a
16 cpu alpha is child's-play compared to getting machine time on a
T90...



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