[mpich-discuss] (no subject)

[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
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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