# Computer Chess Club Archives

## Messages

### Subject: Re: Beating MTD(n,f)

Author: Tony Werten

Date: 00:44:44 06/08/01

Go up one level in this thread

```On June 07, 2001 at 16:04:49, Dann Corbit wrote:

>On June 07, 2001 at 06:52:07, Tony Werten wrote:
>>On June 06, 2001 at 10:32:14, Gian-Carlo Pascutto wrote:
>>>On June 06, 2001 at 09:06:40, Vincent Diepeveen wrote:
>>>>Noop it doesn't make it void.
>>>>To get from 100 to 200 is harder as it is to get from 10 to 20.
>>>If they mean the same thing, not at all.
>>>Note that I said you should be taking convergence acceletrators
>>>into account. Every competetive implementation of MTD(n,f) has
>>>them and the papers suggest them so that is a valid requirement.
>>>
>>>If you increase the window forecefull from 100 to 200 when you
>>>are using millipawns it's the exact same thing as increasing it
>>>from 10 to 20 when you are using centipawns.
>>>
>>>If you rely purely on the fail-soft and do not adjust the bounds
>>>with the accelerators, I think you are right, but I really would
>>>like to see evidence of it. When forcing the bounds it's just the
>>>same thing however, and that is what every good MTD(n,f) implementation
>>>is doing.
>>>
>>>You are basically saying that the difference between 0.1 and 0.2
>>>is different from that between 0.1 and 0.2. No it's not :)
>>
>>I think what Vincent is saying is that there's a difference between 0.1 and 0.2
>>and 0.10 and 0.20 The first 2 are following each other while the second 2 have 9
>>numbers between them.
>>
>>Suppose the current score is 0.10 Now I find a move with score 0.12 MTD will
>>fail and I have to research. If I had scored 0.1 then the new move would have
>>also been 0.1 and MTD wouldn't have to research.
>>
>>Of course is this not only true for MTD, but for all minimum window searches,
>>but in MTD the first (best) move is also done with mws and this is most of the
>>time the one that has the fluctuating scores.
>
>I imagine that this is a stupid question, but what happens if we simply truncate
>on the test to research?  We could just reorder the moves at that point instead,
>if the difference is tiny.

Not a stupid question.

I was thinking about something like this. If I have time I'll test this weekend.
( I'm messing with my code to get out the bugs )

My idea is this: I like the millipawn stuff, because I can give small bonusses
to things I like ( not nescessairily correct ). When I return from the
evaluation I could divide it with 10, 100 or whatever. This would mean the
millipawn stuff still works (since 10 millipawns is still 1 centipawn ) but my
search might have more cutoffs.

Tony

PS About my code. I found out that if I take a testposition and I mirror it, I
get a different solutiontime ( even with material only eval ) I think it's in
the extension discision part.

Others might try if their engine doesn't have this problem.

```