Hello:
I just installed OpenMPI 4.0.5 on a Linux machine running Pop!_OS (made by
System76). The workstation has the following architecture:
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
Address sizes: 39 bits physical, 48 bits virtual
CPU(s): 16
On-line CPU(s) list: 0-15
Thread(s) per core: 2
Core(s) per socket: 8
Socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
I am trying to run on the Linux box a code that I usually run on a Mac OS
without any issues.
The script that I use is:
exe='/usr/bin/mycode' # on jp2
mympirun='/opt/openmpi/4.0.5/bin/mpirun' # GFortran on jp2
$mympirun -np 12 $exe input1
I get the following error:
====================================================
No protocol specified
--------------------------------------------------------------------------
There are not enough slots available in the system to satisfy the 12
slots that were requested by the application:
/usr/bin/mycode
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.
=======================================================
I do not understand “slots”. The architecture description of my Linux box
lists sockets, cores and threads, but not slots.
What shall I specify instead of "-np 12”?
Thank you,
Paul
