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Subject: Re: Parallel search

Author: Bruce Moreland

Date: 11:41:57 08/06/99

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On August 06, 1999 at 13:47:35, Brian McKinley wrote:

>I am implementing a parallel search, and I have 2 questions for those who have
>gone before me.
>
>1. If my parent thread has searched all moves at a ply and a child thread is
>still searching, should the parent thread wait for the child thread to return,
>or should it abort the search in the child thread and re-search the move from
>the parent?  This would allow the child thread to be placed back in the pool so
>that both threads are working again.  I am assuming that the re-search would be
>fast to the point where there child was stopped.

I didn't try this.  What I did instead was add a free thread to my generic
thread pool, then block and wait for that.  This lets the original thread
continue, and allows other threads to ask for help if they need it.

>2. If a score comes back that is greater than alpha and less than beta and there
>is a child thread searching another move for this ply, should I update beta in
>the child thread?  Am I correct in assuming that this is not an issue for MTDf?

I don't know.  In my program I ignore this problem, although I have to be
careful not to consider a move to be a PV or fail high move just because its
score came back higher than the original alpha, since alpha may have increased
since it started searching.

bruce

>
>
>-- Brian McKinley



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