Author: James B. Shearer
Date: 10:16:39 10/09/99
Go up one level in this thread
On October 08, 1999 at 08:50:37, Robert Hyatt wrote:
>James... a quick note about your games last night.
>
>I noticed that you played a huge match vs "scrappy" on fics... 70 games
>total. And that out of the 70 games, I found 1 draw and 1 loss. Except
>for the last 3 games, you were playing Crafty as it ran pretty much all
>by itself on the quad pentium pro/200 machine. I have an exam scheduled
>for early next week, and the current programming assignment was due yesterday
>at 5:30pm, so at that time, I 'disallowed' logins on the quad P6 box to
>encourage students to not play around and get ready for the test.
Actually I had 3 draws (and 1 win) in 73 games. I think this is a bit
below my expectation (of perhaps 4 points).
Drawing 0 increment games against a computer is not so easy. In this
regard it is polite of crafty to offer a draw in KR vrs KR instead of playing on
for 50 moves.
>What you saw last night was the 'real' scrappy without any student programs
>running. Scrappy normally runs at "nice 20" so that it doesn't influence any
>student programs that get run, but they definitely kill it when they are
>running. The last 3 games were on a loaded system, if you could tell the
>difference, as the backup process started running in the middle of the night,
>and while it is only one process, it hurts crafty significantly, because I do
>run 4 threads, and 4 threads on 3 cpus (still using nice 20 all the time) is
>(for me) an absolute performance killer, usually being slower than if I used
>only one much slower cpu.
I probably wasn't at my best for the last few games either.
>If you want to play such a match vs crafty, on the quad xeon, that is easy to
>set up and in general, the quad xeon will be 100% dedicated to playing chess
>since it is my machine and I can simply stay off of it during such a match. It
>is about 2x faster (at present, although I am waiting on Intel to ship the 600
>xeons at the end of October so that I can upgrade the processors to make it
>about 50% faster again).
>
>As I had told you, without students on that box, it is a tough opponent. The
>xeon is tougher and will become tougher still, soon. But it is _very_ difficult
>to draw/win vs even the quad P6 unless you are an IM, when playing at blitz time
>controls. And even then the wins are very few and far between.
>
>If you want to try the xeon, let me know.
>
>BTW the last game (the one you won) was exactly the right kind of strategy for
>a bogged down machine... the ending position was a 'null-move killer' type
>position as it was generally doing 3-4 plies for 90% of that game, where it was
>normally doing 9-12 plies in most of the others...
The last game was a typical win vrs a computer. The computer already
one pawn up, grabs another on the queenside and gets mated on the kingside.
However I don't understand the 3-4 plies bit. Even if you were slowed
down by a factor of 4 this would be 1-2 plies so you should still have been
getting 7-10. The losing move was 25 Qxb7. Checking with crafty v16.19 Qxb7 is
selected through ply 8, fails low and is eventually rejected in ply 9.
Scrappy's move 27 qc7 was also inferior allowing mate in 5. Again checking with
crafty v16.19, qc7 is first selected in ply 5 then fails low (quickly resolving
to -Mat05) in ply 8 and is eventually rejected. Scrappy apparently saw it was
in trouble as it took 29 seconds on this move (3 times as much as any other) but
was unable to find a better move in time. This is consistent with a depth of
7-10 plies.
I think you have an absolute upper bound on search time but in a case
like move 27 where scrappy sees the move it's going to play gets it mated and
still has some time (almost 3 minutes here) it might be better to keep searching
a while. In this case scrappy was still dead lost, although it had a couple of
moves which avoided the mate in 5. However that didn't have to be the case, it
could have had a saving move that it didn't find in time.
James B. Shearer
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