Author: Dann Corbit
Date: 12:09:25 02/19/04
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On February 19, 2004 at 14:55:40, Robert Hyatt wrote: >On February 19, 2004 at 14:25:07, Dann Corbit wrote: > >>On February 19, 2004 at 14:14:11, Robert Hyatt wrote: >>[snip] >>>Clusters can work. 1000 nodes is a totally different problem from using 1-64, >>>but nothing I see says it is an impossible task. Impossible to "some" perhaps >>>so. Lots of things are impossible to "some". Fortunately, for the rest of us, >>>what is "impossible" is something that just takes a bit longer to do... :) >> >>A cluster notion (e.g. 64000 machines maybe using the network): >> >>Divide the machines into clumps that work on forward nodes, and multiple >>possible best moves. > >I already do this on large SMP platforms. IE crafty has a "group" concept, so >that with (say) 64 nodes, you don't get 64 nodes working on one split point. >That is bad for multiple reasons. Usually there are not 64 moves to search so >the split overhead is just pure overhead. Also, on NUMA boxes, you don't want >64 processors banging on one "split block" even though they don't do it that >much unless the split is too deep in the tree (this is also controllable in >current crafty). > >I suspect the same idea will be the right way for clusters. Divide it into >groups, sub-groups, and so forth. The "groups" have a "head" and the initial >split is between the "group heads". Then each group head can further split its >tree farther down the path, with sub-group members. Of course each of these >might be a "sub-group-head" that could later further split the tree among >sub-sub-group members. > >I think some such hierarchy is necessary for truly large numbers of processors, >and the potential for search overhead is going to be significant. Have one CPU that looks at the whole tree and makes recommendations (a sort of loadmaster). In that way, the CPU pool does not get divided evenly. So (in the first move example) moves like 1. e4, 1. d4, 1. Nc3 get 20,000 CPUs each and things like 1. a3 might only get 10 CPUs. This concept can also carry forward as far as you like.
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