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Subject: Re: Researching after a deep fail low

Author: José Carlos

Date: 23:58:22 09/24/01

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On September 24, 2001 at 23:41:17, Dave Gomboc wrote:

>On September 24, 2001 at 15:24:53, José Carlos wrote:
>
>>  First, the context:
>>
>>  Last night I finished implementing pondering for the first time. As usual, I
>>chose the easyest way to begin with, until I make sure I understand everything.
>>  So I did it this way: after moving, I guess the opponent move (second of the
>>pv), make it, and start thinking. When the opponent's move arrives, I unmake the
>>guessed move, make the real move, and start thinking normally. I expected the
>>program to get to the pondering depth due to the info in the hash table.
>>  This worked fine most of the time, but when the ponder search failed low deep,
>>the research didn't go straight to that point. Instead, it chose another move at
>>the begginning (because it saw the bad move in the hash table) and went
>>deepening slowly.
>>  I was very disapointed with this behavior, but when I started playing on ICC,
>>I saw a big rating increase. Actually, the explained behaviour turned out to
>>work really good, as usually the program made a good move even with less depth.
>>
>>  Now the question:
>>
>>  Has this been tried in _normal_ search? I mean, restarting from the begginning
>>after a deep fail low.
>>  Is this it a mistake to do what I'm doing? If so, what are the drawbacks?
>>
>>  Thanks in advance,
>>
>>  José C.
>
>Yes, many years ago Jonathan Schaeffer found this method (restarting the search
>after a big fail-low) worked well for him.  Make sure you give yourself enough
>time to get back to a reasonable depth, though (for example, the same depth that
>you found the fail-low at).  Many people don't do it, though, so perhaps they
>have found otherwise.
>
>It's funny that you were initially "disappointed"... why is that?  Did you think
>that your method was a bit of a hack and was doing the wrong thing in this
>circumstance? :-)
>
>Dave

  I was disappointed because I expected the search to get quickly to the point
where the ponder search finished, given the info in the hash table. I thought my
method was wrong, and I must change it, until I noticed that it was actually
working fine.

  José C.



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