Author: Robert Hyatt
Date: 10:16:22 10/08/02
Go up one level in this thread
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...
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