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Subject: Re: Interesting endgame database probe problem

Author: Robert Hyatt

Date: 15:30:17 02/07/99

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On February 07, 1999 at 13:12:01, José de Jesús García Ruvalcaba wrote:

>
>Was crafty using the full 3+2 five men tablebases?

yes...


>If the position after 100...Kc4 is a mate in 70 moves, then the position after
>101.Qe2+ should allow black a move which is a mate in at most 69 moves. But this
>position appeared *twice* before in the game. I wonder why crafty did not go for
>the mate in 69 *before*.


the problem is that at the point where it screwed up, it had a _real_ mate
in 73, or a bogus mate in 70 (bogus because it was a draw before the mate
could be played).  So it went for the mate in 70 because the bug didn't let
it detect that the next opponent move would be a 3-fold repetition.



>
>	Is it possible to have a queue of tablebase positions which need to be scored
>waiting for the harddisk to respond?

not really.  Because when I do a probe, I _know_ I will get a result.  So
the search will definitely terminate here, with win/lose/draw scores.  But I
can't really go on until I know which...  because of alpha/beta....



>Currently there are no faster drives available, but there will...

Certainly, although I doubt we are going to see much below 5ms for the
access time.  There is still 'inertia' to overcome.  But it wouldn't matter
if it was down to 1ms...  because compare a 1ms disk read to a 2ns instruction
cycle time in a 500mhz processor...  a difference of _one million_ that will
only get worse, not better...



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