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Subject: Re: retrieving the PV from hash questions

Author: Richard Pijl

Date: 08:23:23 09/06/04

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On September 06, 2004 at 10:48:00, Stuart Cracraft wrote:

>On September 06, 2004 at 04:47:12, Alessandro Scotti wrote:
>
>>On September 05, 2004 at 22:12:35, Stuart Cracraft wrote:
>>
>>>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.
>>
>>I don't either. But since I get my PV from the hash table, it's already there.
>
>Mine is already in there as well so I don't see why Bob said to
>store it in the hash table after the last iteration unless Crafty uses
>some different method to record the PV and has to store it in the hash
>table prior to the next iteration. Why wouldn't it be in there already?
>Does Crafty clear the hash table between moves?

Reinserting (from a PV array) makes sure that the whole PV is in there for the
next search. The PV positions could have been overwritten by other positions.
Richard.

>For the record, I clear the hash table between moves but only because
>I do suite testing exclusively -- I plan to make this a flag based
>on whether I am testing (clear hash table between each test position)
>or playing a normal game (don't clear hash table.)
>
>In the latter case, with the structure of the program, it walks the pv
>after each iteration to print out the pv. Hence it is already in the hash
>table at the start of the next iteration, so no need to add it. Not sure
>what circumstance would ever require it to be added.
>
>This is why I haven't added it. Structurally it looks unsound for my program.



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