Author: Uri Blass
Date: 20:50:08 11/21/02
Go up one level in this thread
On November 21, 2002 at 22:56:40, Vincent Diepeveen wrote: >On November 21, 2002 at 21:39:06, Uri Blass wrote: > > > >>On November 21, 2002 at 21:21:09, Vincent Diepeveen wrote: >> >>>On November 20, 2002 at 17:51:40, Alessandro Damiani wrote: >>> >>>'verified' nullmove, or in a different implementation but >>>same algoritm, with just 1 ply reduction is nearly a fullwidth >>>search. >>> >>>I did with a bigger reduction of course. that's also very >>>costly compared to R=3. This was just an experiment carried >>>out years ago when it was described in ICCA journal. Now >>>we have same algoritm in a few lines diff algorithm. >>> >>>I do not see how Omid can just suffer 50% slowdown of his >>>algorithm. Note he only publishes search depths not >>>search times. That is wrong. >>> >>>You must publish search times. >> >>I do not see how you can suffer more than 50% slow down. > >Of course you suffer more than 50% slowdown. Every person with >a decent chessprogram will suffer more than 50% slowdown. > >This is trivial. > >>I think that you simply do not understand the algorithm. > >I understand it perfectly well. I have run with it for years. > >So please apologize to me! No I also got results that it is not slow as you describe and I have a good branching factor. > >>The algorithm does not do nearly full width search because after the first >>reduction the search is normal null move pruning without verification. > >Yes it nearly does, it is a reduction of just 1 ply! > >With nullmove you reduce in the same subtree 4 ply. Or with R=2 you >reduce 3 ply! With R=2 you reduce 3 plies in a recursive search. Here you reduce 4 plies after the first reduction and you do the first expensive reduction only in part of the cases. > >Do you understand that with a branching factor of 3.5 that >a search depth of 2 ply more means about a factor of 10 times more >nodes more or less and not factor 2? The big factor is only in part of the cases and the big factor is not a factor of 10 because after the first reduction you never waste time on expensive searches. Suppose that you have a line like 1.e4 null 2.d4 null When you get a fail high after the second null you search to depth-4 and do not verify the fail high by depth-1 search. Uri
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.