Try tests on GitHub Actions with three MPI ranks

[jhale]

Can keep the others on two for coverage? To discuss.

[jhale]

--------------------------------------------------------------------------
There are not enough slots available in the system to satisfy the 3
slots that were requested by the application:

  ctest

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

A "slot" is the PRRTE term for an allocatable unit where we can
launch a process.  The number of slots available are defined by the
environment in which PRRTE 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, PRRTE defaults to the number of processor cores

In all the above cases, if you want PRRTE 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 --map-by :OVERSUBSCRIBE option to ignore the
number of available slots when deciding the number of processes to
launch.
--------------------------------------------------------------------------

https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners/about-github-hosted-runners#standard-github-hosted-runners-for-public-repositories

Strange as the public runners all have at least 3 processors.

[jorgensd]

--------------------------------------------------------------------------
There are not enough slots available in the system to satisfy the 3
slots that were requested by the application:

  ctest

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

A "slot" is the PRRTE term for an allocatable unit where we can
launch a process.  The number of slots available are defined by the
environment in which PRRTE 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, PRRTE defaults to the number of processor cores

In all the above cases, if you want PRRTE 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 --map-by :OVERSUBSCRIBE option to ignore the
number of available slots when deciding the number of processes to
launch.
--------------------------------------------------------------------------

https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners/about-github-hosted-runners#standard-github-hosted-runners-for-public-repositories

Strange as the public runners all have at least 3 processors.

Ubuntu runders only have two processors. Mac tynnere have more

[jhale]

Not according to githubs own documentation?

[francesco-ballarin]

That's odd, in multiphenicsx I use 3 slots
https://github.com/multiphenics/multiphenicsx/blob/main/.github/workflows/ci.yml#L74
and I don't seem to have any need to use oversubscribe or similar options

[jorgensd]

Not according to githubs own documentation?

are we reading the same documentation?

[jhale]

No, there are two sections, one for public repositories and one for private. You are reading the latter.

[jorgensd]

No, there are two sections, one for public repositories and one for private. You are reading the latter.

Interesting! That is a new development?

I had the same oversubscription issue when using openmpi with adios4dolfinx a while back. I haven't seen it with mpich before.