Author: James Swafford
Date: 11:40:12 10/13/02
Go up one level in this thread
On October 13, 2002 at 14:25:00, Vincent Diepeveen wrote: >On October 13, 2002 at 12:00:39, Andrew Williams wrote: > >It was answerred another 2 times that it's 12 ply simply, >excluding qsearch+extensions. So the hardware is inside that >12 ply, but the hardware depth FROM that 12 ply can be UP to >6 ply. So it isn't always searching 6 ply in hardware. It's >a variable depth which they can do in hardware. That explains >probably extensions around mainlines with captures very well >and do not forget that the chips could do up to 1 billion nodes >a second in theory. Ok, if you say that was answered, I believe you, but that doesn't sound like what the quote I responded to in a thread below meant. Can you provide the transcript for this? Seriously, I would very much like to see it. > >It searched on average over a period of 3 minutes only 126 MLN >nodes from that. that's only 10% effective usage or so each >chip. That means that there are *always* loads of chips idling. > >So getting extra processors to the PV is a very clever thing to >do then. Of course you give the chips a small search depth then. >2 to 3 ply is what Brutus was using at world champs 2002. Bigger >search depths in hardware were too inefficient. > >You cannot use killermoves in hardware and you cannot use hashtables >and Hsu didn't use nullmove either. With his last so many plies pruning >(whatever name you want to give it, razoring, futility pruning) that means >that when searching the Principal variation, you have to give many processors >small search depths, because the pruning around principal variation is >a lot less than for the other moves. > >It would be interesting to hear in a next chat how many plies the forward >pruning was in the hardware part. Here just doing 1 or 2 ply didn't >reduce anything. Yet i remember some statement from a talk at M$ from >Hsu recently where (was it Tom kerrigan) asked Hsu about forward pruning >in the hardware chips and he answerred he was doing that. > >So what type of pruning he did there is not so interesting. Interesting is >that it saved them up to 90% nodes in hardware. That's very clever, because >chrilly concluded that without forward pruning in hardware, your tree gets >just TOO huge (because move ordering is near random). > >Chrilly uses nullmove. If Deep Blue used something else there. Only >interesting thing from my viewpoint therefore is to know how many plies >they did this forward pruning in hardware. > >My own experiments are not relevant here too much, because i use hashtable >and nullmove everywhere. So it is very well possible that without nullmove >the effect of forward pruning is way bigger than without. > >>Several people asked: >> >>Question: What does "12(6)" mean in Deep Blue's logs? >> >>Dr Hsu said, "12(6) means 12 plies of brute force (not counting the search >>extensions & quiescence). 6 means the maximum hardware search depth allowed. >>this means that the PV could be up to 6 plies deeper before quiescence." >> >>Unfortunately questions were being fed through a third-party, so it wasn't >>possible to get a follow-up. >> >>Andrew
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