Author: José Carlos
Date: 07:15:46 09/25/01
Go up one level in this thread
On September 25, 2001 at 09:58:59, Robert Hyatt wrote: >On September 25, 2001 at 02:58:22, José Carlos wrote: > >>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. > > >When you think about it, it could not. That deep fail low table entry will >re-shape the entire shallow search tree and make you traverse parts of it that >you quickly skipped on the first search. But now you are doing a more informed >search (you have a piece of information you didn't have the first time) so you >should expect that hash hits are not going to get you back to the last iteration >quickly. Yes I understand it now. But when I saw it for the first time, I was surprised. Just a thought and everything looks logical. José C.
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