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Subject: Re: Hash move question

Author: Bob Green

Date: 08:49:53 08/18/01

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On August 18, 2001 at 01:21:30, Robert Hyatt wrote:

>
>None of the above.  :)
>
>first, check hash entry to see if you can avoid searching, by looking at
>the draft, the bount stored, etc.  If you can stop searching, then you are
>done.

I'm not sure what "draft" and "bount" (or is bount=bound=alpha cutoff?) are.
I've not seen these terms before.  Could you explain them please?

I read this to create the hash of the current position (pre-move generation) and
index into the hash table.  If the hash checksum matches then get the
{alpha|beta|exact} score for the position, which may cause a cutoff.  Did I get
it right?  Oh - is draft == plydepth?

>
>If the draft is insufficient, or the bound is useless, then you look to see if
>a move (best move) was stored in the table.

When would a best move not be stored?  This portion is unclear to me.  I thought
that the hash was created/saved after the alpha/beta call and during the fail
high/low/exact determination.  Shouldn't in every case the move that was just
made/unmade be the move to be stored with this position?

<If so, make it and search, without
>doing a move generation.  If that move causes a cutoff, then you just got a
>cutoff without using your move generator at all, which is a significant savings
>of computation operations.  If you don't get a cutoff, then you generate
>captures and try the good ones,  etc...
>
>The trick is all about avoiding the move generation...



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