[Parth1999]

Hi
I am using hp z6 g4 workstation which has two processors, each having 20 cores
but while typing lscpu it showing only 20cores, and 1 processor, how can i use other processor and its core also
because in system properties it clearly shows 2 processors. I am only able to break down in 20 subdomains


pls help

[olesen]

Originally Posted by Parth1999

Hi
I am using hp z6 g4 workstation which has two processors, each having 20 cores
but while typing lscpu it showing only 20cores, and 1 processor, how can i use other processor and its core also
because in system properties it clearly shows 2 processors. I am only able to break down in 20 subdomains


pls help

lscpu reports information about the CPU. Presumably both of your cpus are identical, so it only lists information about one cpu type. This is the same on my machine (also dual socket).
If you instead examine the output of "cat /proc/cpuinfo" you will see information on a per thread basis. Pay attention to the following fields in that output (physical id, core id, cpu cores, siblings). If you have hyperthreading enabled, you will notice that the core id appears twice on each processor.


But you don't need to worry about any of that. Just use mpirun -np NUMPROC when starting your jobs, MPI will take care of the rest.

[Parth1999]

Originally Posted by olesen

lscpu reports information about the CPU. Presumably both of your cpus are identical, so it only lists information about one cpu type. This is the same on my machine (also dual socket).
If you instead examine the output of "cat /proc/cpuinfo" you will see information on a per thread basis. Pay attention to the following fields in that output (physical id, core id, cpu cores, siblings). If you have hyperthreading enabled, you will notice that the core id appears twice on each processor.


But you don't need to worry about any of that. Just use mpirun -np NUMPROC when starting your jobs, MPI will take care of the rest.

Hi
tried this i typed mpirun -np 40 mydisFoam -parallel
earlier i was using 20 instead of 40

but im getting this error



There are not enough slots available in the system to satisfy the 40
slots that were requested by the application:

intraVenFoam

Either request fewer slots for your application, or make more slots
available for use.

A "slot" is the Open MPI term for an allocatable unit where we can
launch a process. The number of slots available are defined by the
environment in which Open MPI processes are run:

1. Hostfile, via "slots=N" clauses (N defaults to number of
processor cores if not provided)
2. The --host command line parameter, via a ":N" suffix on the
hostname (N defaults to 1 if not provided)
3. Resource manager (e.g., SLURM, PBS/Torque, LSF, etc.)
4. If none of a hostfile, the --host command line parameter, or an
RM is present, Open MPI defaults to the number of processor cores

In all the above cases, if you want Open MPI to default to the number
of hardware threads instead of the number of processor cores, use the
--use-hwthread-cpus option.

Alternatively, you can use the --oversubscribe option to ignore the
number of available slots when deciding the number of processes to
launch.


pls help

[olesen]

Just like the help says:

Alternatively, you can use the --oversubscribe option to ignore the
number of available slots when deciding the number of processes to
launch.