On 09/ 4/10 12:10 AM, Simon King wrote:
Hi David!
On 4 Sep., 01:01, "Dr. David Kirkby"<david.kir...@onetel.net> wrote:
Be aware, that for hyperthreaded machines, the number of CPUs may exceed the
number of cores.
Ah. I guess that I wanted the number of cores. If, as you say, half
the CPUs is enough to occupy all resources,
It depends on the machine. I have here a couple of quad processor machines,
which only have one core. So in that case, to use all resources one would use 4
threads.
In the case of machine with 2 or more threads per core, you will use a very
large fraction of the resources by simply using the number of cores.
then I'd probably use
something like
@parallel(ncpus=os.environ.get('SAGE_NCPUS') or 2)
so that at most 2 (or another small number) parallel processes are
created, unless the user requires otherwise, by setting an environment
variable.
Cheers,
Simon
Is SAGE_NCPUS used anywhere?
I think SAGE_NUMBER_THREADS is more useful. Someone had proposed
SAGE_NUMBER_THREADS_atlas would override a default value and work for ATLAS
only. So you could have SAGE_NUMBER_THREADS_gap or something like that. So there
would be
SAGE_NUMBER_THREADS # For everything unless one of these below is set
SAGE_NUMBER_THREADS_gap
SAGE_NUMBER_THREADS_atlas
etc etc
I don't think we have actually used any of this yet.
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