[mpich-discuss] (no subject)

[Ricardo Román Brenes]

Those xeon have hyper threading technology. They sell then as double the
real core they have.
On Feb 4, 2014 10:53 AM, "Reuti" <reuti at staff.uni-marburg.de> wrote:

> Hi,
>
> Am 04.02.2014 um 17:45 schrieb Andreas Gross:
>
> > I am looking for help with MPICH2.
> >
> > I installed mpich-3.0.4 on a Centos 6.5 PC with 24 cores.
> > When I launch with mpiexec on 17 procs all procs are running 100%.
> > When I launch on more than 17 procs the job gets slower and most
> processors run on less than 100%.
> >
> > I spent a lot of time google'ing this problem but did not find any
> answers.
> > Somebody said it may be a memory problem but the computer has 32GB RAM
> and the same problem occurred when running a very small problem.
> > On bigger computers I have run the same code on 2,048 processors with no
> problem at all.
> >
> >
> >
> > "lscpu" gives the following response:
> >
> > Architecture:          x86_64
> > CPU op-mode(s):        32-bit, 64-bit
> > Byte Order:            Little Endian
> > CPU(s):                24
> > On-line CPU(s) list:   0-23
> > Thread(s) per core:    2
>
> There are only 12 real core. Depending on the application it might degrade
> when the threads are used. For our applications I found it might be around
> factor 1.5 which can be used - this matches your detected limit of 17.
>
> -- Reuti
>
>
> > Core(s) per socket:    6
> > Socket(s):             2
> > NUMA node(s):          2
> > Vendor ID:             GenuineIntel
> > CPU family:            6
> > Model:                 45
> > Stepping:              7
> > CPU MHz:               1200.000
> > BogoMIPS:              4590.92
> > Virtualization:        VT-x
> > L1d cache:             32K
> > L1i cache:             32K
> > L2 cache:              256K
> > L3 cache:              15360K
> > NUMA node0 CPU(s):     0-5,12-17
> > NUMA node1 CPU(s):     6-11,18-23
> >
> >
> >
> > "less /proc/cpuinfo" shows:
> >
> > processor       : 0
> > vendor_id       : GenuineIntel
> > cpu family      : 6
> > model           : 45
> > model name      : Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz
> > stepping        : 7
> > cpu MHz         : 1200.000
> > cache size      : 15360 KB
> > physical id     : 0
> > siblings        : 12
> > core id         : 0
> > cpu cores       : 6
> > apicid          : 0
> > initial apicid  : 0
> > fpu             : yes
> > fpu_exception   : yes
> > cpuid level     : 13
> > wp              : yes
> >
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