[Arumugaraj]

My processor consists of 24 cores and 48 threads and I am able to run OpenFOAM simulation in parallel using the command

mpirun -np 24 icoFoam -parallel

upto 24 logical processors above which (for example 42) it is showing the following error. I am rookie in openFOAM.

Invalid MIT-MAGIC-COOKIE-1 key--------------------------------------------------------------------------
There are not enough slots available in the system to satisfy the 42
slots that were requested by the application:

icoFoam

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.
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[zeyamiao]

I’m a student in China,and May I ask how you resolved it later~

[cececerece]

Hello! First of all, You should specify number of regions in DecomposeParDict according to the number of cores you want to use (I am sure you did this, but still it's important to note).

Also, I am trying to make a parallel simulation myself right now and I have found this presentation. From it, it looks like OpenFOAM package does not support hyperthreading and you should specify only the number of physical cores (which is 24 in your case as it seems).

Hope it helps! However, if anyone knows better, I would be glad to know too