[mpich-discuss] (no subject)

[Reuti]

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
> 
> _______________________________________________
> discuss mailing list     discuss at mpich.org
> To manage subscription options or unsubscribe:
> https://lists.mpich.org/mailman/listinfo/discuss