Computer Chess Club Archives




Subject: Re: Can that really work?

Author: Dann Corbit

Date: 18:34:10 03/07/06

Go up one level in this thread

On March 07, 2006 at 20:49:11, Mark Boylan wrote:

>On March 07, 2006 at 20:42:18, Marc D wrote:
>>On March 07, 2006 at 20:37:55, Mark Boylan wrote:
>>>On March 07, 2006 at 20:18:18, Marc D wrote:
>>>>I still think Rybka has preconfigured chess data knowledge in it's code to
>>>>acomplish these things.
>>>I don't understand.
>>>All of the better programs that I've read have preconfigured chess knowledge of
>>>some sort for evaluating positions.
>>>Are you saying that Rybka has a precalculated table containing the evaluations
>>>of some common positions? Like a middlegame book? Would that even help beyond
>>>the opening. Even if it did, would it be bad?
>>>Whatever that program does, it's damn clever.
>>Yes something similar like this.
>>But i agree with you that what the program does is quite clever and makes it so
>>far unbeaten.
>I certainly don't know what I'm talking about, but it seems to me that the
>chance of getting a hit on a fixed set of positions beyond the opening is so
>slim as to make it not worth the effort. Do any other programs do that?

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.

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