Computer Chess Club Archives




Subject: Re: Can that really work?

Author: Nathan Thom

Date: 19:12:42 03/07/06

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On March 07, 2006 at 21:34:10, Dann Corbit wrote:
>Opening books hold the frequently played positions near the origin.
>If we are talking about some position 50-60 plies down the road, the odds of
>hitting it during game play are "astronomical".  No, they're "commical" -- and
>Just the bare positions -- ignoring half-move clock and 3-time repeat are 10 to
>the 50th power.  So, let's suppose that our intrepid programmer analyzes one
>billion positions.  The odds in hitting one of them are one in ten to the
>forty-first power.  Not good.  Plus you would have a bit of bloat storing the
>positions and a bit of time spent searching for them.
>Now, let's suppose that we bypass all these objections and say "What the heck,
>let's do it anyway!"
>Well, when we look at memory, we will see (one billion * hash element size)
>bytes of memory consumed.  A very small hash entry would consume 16 bytes but
>we'll say he's clever and stores only 8 bytes.  That would be 8 gigs of ram.
>"Well..." (you may retort) "perhaps they are loaded on demand."
>I suppose that a page fault for every new position would slow down the program
>so much that we would see 50-100 NPS at best.  While Rybka may be a slow
>searcher (let's not start that debate) it's certainly not that slow.
>I suppose we're just going to have to admit that V.R. is a clever guy, and that
>he hasn't stored the middle game in the computer's data segments.

What about only considering parts of the board (<64 squares) or only specific
pieces. e.g. only consider rooks+kings and have a pre-generated table of the
most common situations and best move? Sure, the other pieces which have been
ignored could make the move ridiculous or illegal but i wonder what kind of
success rate this would give?

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