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Subject: Re: shredder 8 and weird PVs? (sandro?)

Author: Sune Fischer

Date: 10:22:18 01/20/04

Go up one level in this thread


On January 20, 2004 at 12:01:59, Robert Hyatt wrote:

>Then Grandmasters are producing tons of "eye candy" every day as they
>merrily annotate games and give variations.  Are you really a chess player?
>IE I want analysis, not just "white is better" myself.

Yes I am really a chess player, and I know how to analyze using an engine.

You need to go back and forth down the lines that look interesting.

Particularly big sacrifices can take a while for engines to see, they fail high
10 times faster if you just execute the move so nullmove and other pruning
devices gets a better root window to work with.

>>It never shows you all the refutations, say there is a queen en prised on the
>>board, the PV at iteration 5 shows us taking it but at ply 6 we get a completely
>>new line.
>>Why can't we take the queen, what's wrong with that, what did the engine see?
>
>
>That is obtainable, if you want to know.  You just step down the PV to the
>point in question (you _do_ have a PV to step down, right, otherwise you would
>not even know the queen is hanging except by the score maybe) and then let the
>search show you the PV for the move you are questioning.

If you have lost the first half of the pv how are you going to track it?

>>
>>That's what I want to know, as a chessplayer :)
>>
>
>Me too and that is what I get by having the PV displayed.  With just a best
>move or best move and sometimes random moves below it being shown, I have a
>harder time.  Just note the people that started this thread.  Obviously it
>meant something to them...

Looks to me like Shredder is a bit of an extreme example.
You have the same problem though if you can't resolve a fail high, no pv :)

>Mine almost always goes to the leaf position.  On occasion it gets cut short,
>but that is the exception rather than the rule.

Even after the search has being going on for a while and there are lots of good
hash entries?

>In tactical positions I trust the PV to the end.  IE mate in 15 is not going
>to be flakey near the end.  Nor is winning a pawn or piece, or promoting
>something...
>
>So it is not as useless as you seem to think.

The hash shows the same behavior on tactical positions.

-S.



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