[Beowulf] 1 multicore machine cluster

Mark Hahn hahn at mcmaster.ca
Wed Apr 29 12:38:56 PDT 2009

>> I think the term ´node¡ is a loaded term in HPC.  This is what comes

I think it's just a bit sloppy or at least contextual - I've never
heard it used for anything other than "box".  a node on a conventional
message-passing cluster is clearly one computer, which may contain 
multiple cores, but has a single memory domain.  on an Origin/Altix,
people seem to prefer "brick", but sometimes use "node", and is obviously
not a single memory domain.  MPI programmers usually use "rank" or
"processor", and don't get hung up on nodes.

> There is an awful lot of software around which refers to "nodes" when in
> your nomenclature it means core[1], most of it harks back to when nodes

hmm, a contrary example is gromacs - it explicitly talks about nodes
but permits threads within a node.  ie, an 8-core box could be a single
node with 8 threads or 8 nodes, 1th each.

incidentally, any gromacs experts comment on scalability of using 
the thread support?  (ie, for four 8c boxes with IB, 32 nodes vs 
4 nodes, 8 threads each?)

> had one CPU and a CPU had one core.  Even the concept of cores
> themselves are only six or seven years old, before then a CPU was just a
> CPU and you would refer to "a N CPU cluster".

and to be on the safe side (wrt forms of simultaneous multi-threading),
we should probably try to use "thread" instead.  meaning a single 
hardware execution context.

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