Computer Chess Club Archives




Subject: Re: MTD is a big disaster

Author: Vincent Diepeveen

Date: 23:28:26 07/20/99

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On July 20, 1999 at 11:25:07, Dan Homan wrote:

>On July 20, 1999 at 08:52:18, Vincent Diepeveen wrote:
>>Let's however write down some facts why my prog is unhappy with MTD.
>>It's up to others to generalize it to their progs:
>>  - the huge number of researches needed. In DIEP my evaluation is nowadays
>>    in 1/1000 of a pawn. For a long time i had 1/200 of a pawn (in the time
>>    i experimented with MTD), but now i have 1/1000 of a pawn. So a drop
>>    of 0.20 pawn, which is a normal drop in DIEP, is in fact a drop of 200
>>    points. Happy researching!
>Even if the score dropped a whole pawn (1000 points in DIEP), this would
>only be 10 or 11 zero-width searches (2^10 = 1024) assuming that you

Man 10 or 11 researches,
are you reading what you write?

10 or 11 researches.

In 10 or 11 researches with PVS i should search 11 ply deep
with some luck!

IN PVS getting PV is very smartly with unlimited window. NO

My proggie directly picks a line with a reasonable good alfa,
so it's not wasting much nodes on this.

Of course 10 or 11 researches with MTD means first 9 or 10
researches i'm wasting bigtime nodes!

>bound the score in an efficient manner.  Also,  I can understand having
>a high resolution within the eval routine itself, but does it really help
>to have the output of the eval be in 1/1000 pawn units?  I wouldn't trust
>the sum total of any eval routine to 0.001 pawns! Maybe you could
>output the total eval in units of 1/100 of a pawn (or even less).
>Actually, that is an interesting question.  Does anyone know what the
>optimum eval unit is for searching?  I am talking here only about what
>the eval outputs - not the unit used internally for calculating the eval.
>I know that most programs use the same unit for both purposes, but I
>wonder if that is really optimum.
> - Dan

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