Author: Uri Blass
Date: 10:26:52 10/08/02
Go up one level in this thread
On October 08, 2002 at 13:16:22, Robert Hyatt wrote: >On October 08, 2002 at 12:22:30, Uri Blass wrote: > >>On October 08, 2002 at 12:10:41, Robert Hyatt wrote: >> >>>On October 08, 2002 at 10:55:29, Uri Blass wrote: >>> >>>>On October 08, 2002 at 10:50:20, Robert Hyatt wrote: >>>> >>>>>On October 08, 2002 at 07:08:51, Uri Blass wrote: >>>>> >>>>>>On October 08, 2002 at 00:52:38, Eugene Nalimov wrote: >>>>>> >>>>>>>Wrong. >>>>>>> >>>>>>>Today I visited the talk by Feng-Hsiung Hsu he gave at Microsoft. Here are some >>>>>>>points from memory: >>>>>>> >>>>>>>They used forward pruning in the hardware, and according to Hsu it gives them >>>>>>>5x-10x speedup. He wrote about that in the book, too, but without any details. >>>>>> >>>>>> >>>>>>Can you ask him if 12(6) really means 12 plies in the software and 6 plies in >>>>>>the hardware? >>>>>> >>>>>>A second question is if the plies in the hardware were selective search from the >>>>>>first ply. >>>>>> >>>>>>>In the talk he named that pruning as "analogy cutoff" and mentioned that "if the >>>>>>>move is useless in some position, it is also useless in the similar position". >>>>>>>In the book he writes "it can be done in the hardware as long as it does not >>>>>>>have to be 100% correct". >>>>>>> >>>>>>>They used null-move thread detection, as well as not only singular extension, >>>>>>>but also extension on only 2 or 3 good replies. They used fractional extensions. >>>>>>>He also says that their Q-search is much more powerful than the one that is >>>>>>>usually used in the software-only programs. >>>>>>> >>>>>>>Hsu gave some details why they don't use null-move: >>>>>>>(1) He thinks that singular extensions and null-move gave more-or-less the same >>>>>>>rating difference (100-200 points IIRC). >>>>>> >>>>>>I think that he underestimates null-move pruning. >>>>>> >>>>>>I believe that for long time control null move pruning gives more than 100-200 >>>>>>points. >>>>>> >>>>>>People may try Fritz with selectivity=0 to find it's rating without null move. >>>>>> >>>>>>Uri >>>>> >>>>> >>>>>I can assure you it doesn't. Several of us ran this experiment in the past. It >>>>>produced a 50-100 >>>>>point improvement at most. Bruce ran it first. I then repeated it to see if >>>>>his result held for me >>>>>as well. 50-100 is nothing to sneeze at of course... But that is all it will >>>>>give... >>>> >>>>What was the time control and the hardware. >>>> >>>>I believe that the improvement is bigger >>>>at slower time control. >>>> >>>>If the experiment was some years ago and >>>>in time control that is faster than 120/40 >>>>then the results may be different today. >>>> >>>>Uri >>> >>> >>>I don't know about Bruce. I used 40 moves in one hour followed by 20 moves in >>>30 minutes, >>>with no sudden-death at all. >>> >>>I ran it on several computers here for several weeks... >> >>We have a factor of 2 in the time control. >> >>What was the hardware that was used? >>If the games were played 5 years ago then today we have clearly >>faster hardware. >> >>Uri > > >Pentium pro 200's. I played 2 games at a time on my quad, plus more games in a >linux lab we >had set up. > >yes hardware is faster. No I don't believe that going deeper and deeper >eliminates all the problems >with null-move. I only saw bad problems at depths of 5-6-7-8. I _never_ saw >them pop up at >depths of 12 and beyond, which Crafty could reach in the pentium pro at 1 minute >a move... > >R=2 used to gain at most 2 plies. Yet the overall performance improvement from >my testing >was in the 50-60 point range. Far less than what you would normally expect from >gaining 2 >plies. The conclusion? You aren't _really_ gaining two plies of search depth, >just two plies >reported in the output... I did not say that you get 2 plies of search depth from 2 plies of output but only that I believe that the difference is bigger than 100-200. It may be interesting to repeat the experiment today (you use R=2/3 and not R=2 and it is also important). Uri
This page took 0.01 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.