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Subject: Re: triangular pv vs. hash move pv

Author: Michael Henderson

Date: 12:03:33 09/11/04

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On September 11, 2004 at 14:49:41, Stuart Cracraft wrote:

>On September 11, 2004 at 12:13:36, Sune Fischer wrote:
>
>>On September 11, 2004 at 00:08:20, Stuart Cracraft wrote:
>>
>>>Hi,
>>>
>>>I added keeping a triangular pv in main search and quiescence
>>>to compare it with the output of my walk-the-hashtable-pv.
>>>
>>>The two differ frequently but quite often are also mostly
>>>identical all the way through.
>>
>>Don't forget to check the hash flag, that the moves are actually PV moves.
>>
>>Mostly you get them overwritten with upper or lower moves, those should not go
>>in the PV.
>>
>>>Which should I trust? Seems like the hash table is getting
>>>overwritten with other variations (not sure why). What
>>>kind of scenario would cause that? My algorithm is
>>>length >= depth to replace.
>>
>>That's not a very good replacement scheme, if you only have a single bin I'd
>>recommend using replace always.
>
>This gave a nice improvement on a Thinkpad laptop of 237 solved of WAC
>@ 1 second per, to 244.
>
>I guess recency is more important than depth!!! I don't know why I never
>even considered to replace always. Didn't even test it. I always had
>assumed that depth was more important than recency. Bad assumption
>
>Nowadays, do most use 2-tier or ? If so or whatever, what are the preferred
>replacement algorithms?
>
>Thanks,
>Stuart

Recency is important for short searches in which the average depth is small --
not much overwriting.  Using always replace or depth >= depth exclusively in
tournament games will restrict your depth in many situations.  Most use both (2
tables)--I tested it vs other implementations and I found it's the best.

good luck,
Michael



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