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Subject: Re: Getting a PV using MTD(f)

Author: Andrew Williams

Date: 09:40:02 02/08/00

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On February 08, 2000 at 12:21:18, Tijs van Dam wrote:

>On February 08, 2000 at 11:01:00, Andrew Williams wrote:
>
>>On February 08, 2000 at 08:54:22, Tijs van Dam wrote:
>>
>>>I have been reading about the MTD(f) algorithm that is also used by Andrew
>>>Williams in PostModernist. I want to try it, but it has some things different
>>>than a "traditional" search. I am wondering about the following: how do you get
>>>a PV, or even a move to ponder?
>>>
>>>The best move is obvious: it is the last move that failed high at root. But when
>>>searching that move, all moves in the child position must have failed low. So
>>>which one of them is the best? Andrew, how do you do this?
>>>
>>>My first thought was doing an MTD search with shallow depth from the position
>>>that follows the root move. Or maybe a PVS search?
>>>
>>>Who on CCC has experience using MTD?
>>>
>>>Greets,
>>>Tijs van Dam
>>
>>I use my hash-table to keep track of the PV. If I've found a move at
>>a position whose score is > beta, that move ALWAYS goes into the hash-
>>table. I then rebuild the PV by stepping through these moves. It works,
>>but often you find the end of the PV being truncated.
>>
>>BTW in PostModernist I hash moves in the qsearch as well.
>>
>>Andrew
>
>Thanx, I'll try that. I've just converted my program to a first raw version, and
>the results are so far so good. I think the hashtable storing needs some tuning.
>Is hashing faster than researching the q-search for you?
>
>Tijs

Yes, it seems so. It's so easy to take it out and put it back in that I test
this quite often, and it's always been better with hashing in the qsearch.
Did you have a look at the web page I posted in the "Green List" thread? In
there it describes what you need to do to make your hash-table work with
MTD.

Good luck and please keep us posted.


Andrew



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