Author: José Carlos
Date: 13:55:57 08/20/01
Go up one level in this thread
On August 20, 2001 at 14:30:15, Robert Hyatt wrote: >On August 20, 2001 at 11:56:35, José Carlos wrote: > >>On August 20, 2001 at 09:43:22, Robert Hyatt wrote: >> >>>On August 20, 2001 at 05:22:36, Gian-Carlo Pascutto wrote: >>> >>>>On August 20, 2001 at 04:41:41, José Carlos wrote: >>>> >>>>> Then I tried not doing it in the PV, and the strange things went out. The tree >>>>>got smaller and the search deeper. >>>>> I don't know if this is the correct way of doing it (never do a null-move in >>>>>the PV), cause I like to try myself before looking other's sources to see how >>>>>they do it. But looks reasonable. In the PV, we don't expect to fail high, so >>>>>why trying a null move? >>>> >>>>I don't do this, and crafty doesn't seem to be doing this either. >>>> >>>>However, your explanation makes perfect sense and I will try it. >>>> >>>>-- >>>>GCP >>> >>> >>>I used to do it but I found that trying nulls _everywhere_ actually made my >>>tree smaller. I do it this way now because it was more efficient when I >>>tested it.. Not by a lot, but better. >> >> Mmm, some time ago I asked about my not enough deep search, and some of you >>pointed me to the move ordering. I found that null moves in the PV caused the PV >>to go crazy sometimes. So I stoped doint null moves in the PV (according to my >>previous post reasoning) and I did the trick. My fail high on the first >>move/fail highs rate moved from 86-92% to 90-96%. And my search went to 'normal >>depths'. Now I doubt again... Is there something I have to take into account >>when doing null moves in the PV to avoid getting strange PV's? I know, the >>question is too vague but, maybe someone has an idea. >> So, everyone does null moves in the PV? >> >> José C. > > > >I don't see how nulls on the PV can cause "strange PVs". If you have a position >that drives your search nuts, post it and I will run it with Crafty with null >on and off to see how it behaves. > >Null-move definitely causes quirks here and there, particularly false fail highs >if you use PVS and you have to handle them correctly or blow up. I'll recompile the program as it was before and try to find an example, but it was very difficult to catch it, because the strange things happened in games, not in test positions. It must have something to do with hasing too. Anyway, I'll try to find and example and post it here. José C.
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