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Subject: Re: PV Generation by GUI [or IU]?

Author: Robert Hyatt

Date: 21:11:15 12/21/03

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On December 21, 2003 at 11:53:39, Bob Durrett wrote:

>
>I have always assumed that the PV was generated by the engine and that the only
>PV role of the GUI was to display the PV to the human user.
>
>Long ago, I gave up on my wishful thinking that the PV was the best continuation
>or was a continuation leading to the best leaf node.  Nowadays, I wonder what a
>PV really represents.   Maybe in the case of Shredder it is some sort of coded
>message understood only by the programmer?  : )
>
>Could it be that a PV is generated by a process separate from the processes of
>searching and position evaluation?  Maybe the PV generation is initiated when
>some flag occurs and then the normal searching and position evaluation processes
>must be suspended until the PV is sent to the GUI [or IU]?
>


Some do this.  I have no idea about shredder.  But some don't back up a PV
through the engine,  they let the UI probe the hash table to reconstruct the
PV...

And that can lead to some "interesting" PVs from time to time. :)





>Perhaps PVs are sent into some sort of "registers" or holding cells in memory so
>that the GUI can then get the PV information out to the display in an
>asynchronous manner, with the GUI operating independently while the engine is
>still working?
>
>Maybe not all engines do things the same way.

Not maybe.  _guaranteed_.  :)


>
>I would expect a GUI [or IU] to be a good place for picking up the latest
>available PV out of a storage location in memory and then processing the
>information to make it suitable for display.  Maybe the GUI is the right place
>for this sort of processing.  But would the creation of the PV information still
>have to be in the engine?  How do the PV-related tasks divide up between engine
>and GUI [or IU]?
>
>Help!
>
>Bob D.


In Crafty, the engine passes the PV back to the UI for display.  Ditto for
Cray Blitz.  I know others that don't.  Deep Thought/Deep Blue, for example.
There you have to probe the hash table(s) to find the PV moves, and it can
produce some silly-looking PVs at times.




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