Computer Chess Club Archives




Subject: Re: Can that really work?

Author: Dann Corbit

Date: 12:08:42 03/08/06

Go up one level in this thread

On March 07, 2006 at 22:54:09, Vikrant Malvankar wrote:

>On March 07, 2006 at 22:20:35, Dann Corbit wrote:
>>On March 07, 2006 at 22:12:42, Nathan Thom wrote:
>>>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?
>>In the evaluation it would give good success.  But that is what everyone does.
>>As data statements it would have zero usefulness.
>Are current Engines using differant evaluation techniques based on the move no.
>and pieces remaining on the board?

Yes, with different levels of participation in that idea.

Even the most basic programs have "game phase" as part of the eval.

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