Author: Vincent Diepeveen
Date: 18:59:46 09/16/01
Go up one level in this thread
On September 16, 2001 at 09:41:29, Robert Hyatt wrote: >On September 16, 2001 at 06:02:24, Tony Werten wrote: > >>On September 15, 2001 at 22:34:27, Robert Hyatt wrote: >> >>>On September 15, 2001 at 03:28:18, Tony Werten wrote: >>> >>>>On September 14, 2001 at 22:56:06, Pham Minh Tri wrote: >>>> >>>>>I see that dual computers are expensive, not easy to own and still limited in >>>>>power of computing. >>>>> >>>>>I wonder how good / possible if we use all computers in a LAN for chess >>>>>computing. LANs are very popular and the numbers of computers could be hundreds. >>>>>Even though a LAN is not effective as a dual circuit, but the bigger number of >>>>>processors could help and break the limit. >>>>> >>>>>What do you think? >>>> >>>>When you search a chesstree, a lot of times you come into parts of tree that you >>>>have searched before. You either don't want to search this part again ( you have >>>>searched it deep enough before ) or you want to have the best move from the >>>>previous search. Hashtables do exactly this. >>>> >>>>In a LAN (or a cluster) you don't share this hashtable and therefor are >>>>searching the same tree (or parts of it ) time and time again. If you count the >>>>number of nodes searched per second it's a linear speedup but effectively it's >>>>useless. You have to add a lot of computers before you get any real speedup, >>>>specially in the endgame. >>>> >>>>cheers, >>>> >>>>Tony >>> >>> >>>This is not necessarily true. Several programs have distributed the hash table >>>across network nodes. It requires small changes to the basic search algorithm, >>>but a distributed hash table is not only doable, it has been done more than >>>once. >>> >>>I will probably do this in the distributed Crafty when I do it... >> >>I guess sharing the first x ply on a 1 or 10 Gb network will work, but I don't >>think you can use the normal dynamic tree splitting. I gues you have to split at >>a static depth ( decided in the first search ) ? > > > >That is not my intent. Of course, I won't try to split at the deep levels in >the tree that I split at now. But for (say) the first 1/3 of the plies in the >current search, splitting is certainly doable. This will just be a tunable >parameter that will have to be adjusted depending on the hardware and network >speeds. > > > > >> >>Just to get an impression. How many single Xeons do you think you'll need to get >>the same speedup you get on a quad Xeon ? After that, does it scale ? > > >I can't imagine that this will be less than 50% effective. Or, if we take deep >blue as an example, no less than 30% effective. I would think that 8 cpus would >be very close to the quad... > Bob, you're pretty optimistic here i think. A quad xeon delivers 3.1 Now how many single xeons you need for 3.1, well you lose like 50% just like that everywhere we still didn't talk about speedup. then you lose another factor of 6 or so because you can't hash last few plies. Now this factor of 6 is the biggest problem. the system time already isn't the problem. So i would say 3.1 x 6 = 20 nodes at least. O yeah and of course at least a 1.25 gigabit/s network. At a 100mbit network i doubt one ever gets a positive speedup anyway > > > > >> >>cheers, >> >>Tony
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