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Subject: Re: retrieving the PV from hash questions

Author: Stuart Cracraft

Date: 19:12:35 09/05/04

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On September 05, 2004 at 20:46:13, Alessandro Scotti wrote:

>On September 05, 2004 at 20:31:40, Michael Henderson wrote:
>
>>How do you know the real length of the PV?
>
>I don't. I either stop after a few moves or when there is no move for the
>current position (either not in the hash table, or invalid).
>
>>Do you not usually get short PV's due to a hash miss?
>
>Usually I stop because of my 10 plies limit, hash miss is not so common.
>
>>If you don't know the "draft" (due to extensions) at any point in the PV how do
>>you know a hash hit with depth x is good?
>
>I'm not sure I understand this question well, anyway I just ignore the depth
>when retrieving the PV.
>
>>Does score backed up ever really go with the leaf position of the PV?
>
>In my implementation, I wouldn't bet on it. Often I don't even know what the
>leaf is.
>
>>I've heard this method can sometimes lead to blunders in the PV?
>
>Well I have no problems with no-so-good PV's as long as the first move is
>good... and I have had my share of problems for that too!

I walk the PV until there is no further position. No limit. This can then
either be left in the hash table if you don't clear between searches
but like Bob, you should keep the PV entries and restore them in the
hash table before the next search whether or not you table-clear due to
potential changes.

I don't do this. It's a simple fix. I don't know why I've delayed putting
it in.

Stuart




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