Author: Mridul Muralidharan
Date: 03:09:48 09/01/03
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Hi Jeremiah, If you want crafty to get to work with a decent speedup on a 16 or 32 CPU cc-numa where you have say 2 - 4 processors per node with a significant inter-node latency (like most higher cpu numa boxes ?!) , you will have to ensure that the way you split , memory usage , etc is optimal - you dont want to access a hash entry in proc 0 from proc 32 when the latency wil be in milliseconds !!! Hope you are appreciating the real world problems - not theoretical issues. If you actually work on these boxes , you will appreciate the problems faced by these developers more - using threads on such a box for parallelism , urggh !! Regards Mridul PS : Forget getting crafty to work on the 500 CPU beast that Vincent is working on without a total crafty rewrite ! The horrors Vincent must be facing is unimaginable - the once he has already mentioned in this forum and I'm sure , the more horrible ones he may not have ! On August 30, 2003 at 10:40:03, Vincent Diepeveen wrote: >On August 29, 2003 at 23:41:32, Jeremiah Penery wrote: > >>On August 29, 2003 at 18:40:23, Mridul Muralidharan wrote: >> >>>I'm not sure of what/why Prof. Bob Hyatt may have made those comments. But to >>>get a program like crafty to work properly in a numa machine will not be trivial >>>- and it wont be tweaks , but something more. >> >>All multi-CPU Opteron machines are NUMA. Crafty will work just fine in those. >>It will not be theoretically optimal, but that also depends on the OS to help >>with NUMA issues. > >The OS has to do very little for chessprograms. Just keep scheduling the same >process at the same cpu and physically allocating local memory at that cpu's >RAM. > >Of course for a lot of other services the OS has to do a lot different, yet in >chessprograms we do not need it as most of us, except for example cilkchess, >write their parallellism at a very low level. > >>>Duals , etc count as SMP machine not cc-numa which I was refering to. >>Dual Opterons are NUMA. > >And soon all duals that we can afford will be. > >Best regards, >Vincent
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