dual-core amd question

[Francesco Pietra <chiendarret@yahoo.com>]

Question about MPQC job, with command for
multiprocessor with POSIX threads:

 -thread "PthreadThreadGrp>:(num_threads = 4)"

Hardware: Tyan S2895 K8WE with all eigth memory
modules; two dual-core opteron cpus. OS: debian amd64
etch.

The output of a MPQC job says (than the job completes
successfully):

Using ShmMessageGrp for message passing (number of
nodes = 4).
  Using PthreadThreadGrp for threading (number of
threads = 1).
  Using ShmMemoryGrp for distributed shared memory.
  Total number of processors = 4

Why 4 processors? Moreover, with such a system is that
command optimized or should MPI used instead? In other
words, is my arrangement "shared memory" or should be
considered a cluster? 

That because someone has recently warned me that
"dual-opteron is not shared memory [I knew that of
course].  Each cpu has its own memory, and they can
access each other's. If your program uses MPI then
that's the best way of having it."

I had no doubt, until now, that the above arrangement
of memory modules makes my system shared memory.
Cannot try MPI because the progran is not compiled for
clusters.

Thanks for your kind attention.

francesco pietra


 
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