## Cobaya error MPI disabled

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
Karim M
Posts: 1
Joined: June 17 2022
Affiliation: UNAM

### Cobaya error MPI disabled

Hello,

I've been trying to run a simple example from Cobaya using MPI.
However, the MPI apparently is not working because if I run the example using 4 cores as:

Code: Select all

 mpirun -n 4 cobaya-run gaussian.yaml 
The following error is displayed (4 times appears in this case):

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-------------------------------------------------------------
[output] *ERROR* File %s is locked by another process, you are running with MPI disabled but may have more than one process. Note that --test should not be used with MPI.
[exception handler] ---------------------------------------

Traceback (most recent call last):
File "/home/karimpsi/.local/bin/cobaya-run", line 8, in <module>
sys.exit(run_script())
File "/home/karimpsi/.local/lib/python3.9/site-packages/cobaya/run.py", line 203, in run_script
run(info, **arguments.__dict__)
File "/home/karimpsi/.local/lib/python3.9/site-packages/cobaya/run.py", line 130, in run
out.check_and_dump_info(info, updated_info, check_compatible=False)
File "/home/karimpsi/.local/lib/python3.9/site-packages/cobaya/mpi.py", line 274, in wrapper
result = method(self, *args, **kwargs)
File "/home/karimpsi/.local/lib/python3.9/site-packages/cobaya/output.py", line 312, in check_and_dump_info
self.check_lock()
File "/home/karimpsi/.local/lib/python3.9/site-packages/cobaya/mpi.py", line 230, in wrapper
return func(*args, **kwargs)
File "/home/karimpsi/.local/lib/python3.9/site-packages/cobaya/output.py", line 498, in check_lock
self.lock.check_error()
File "/home/karimpsi/.local/lib/python3.9/site-packages/cobaya/output.py", line 118, in check_error
self.lock_error()
File "/home/karimpsi/.local/lib/python3.9/site-packages/cobaya/output.py", line 93, in lock_error
raise LoggedError(self.log,
cobaya.log.LoggedError: File %s is locked by another process, you are running with MPI disabled but may have more than one process. Note that --test should not be used with MPI.
-------------------------------------------------------------

After that, I am also deleting the output folder before I run the .yaml file again. Unfortunately, I face again the same error.

The machine has Ubuntu 20.04.4 LTS (with 24 cores) and these are the stuff that I am using:
- Cobaya was installed from github repo.
- It is running within a conda environment with python = 3.8
- I have OpenMpi 4.1.3
- I installed the python wrapper mpi4py 3.1.3 by using:

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conda install -c conda-forge mpi4py
(I also tried to install through pip but it keeps displaying the same error).

Moreover, when I run

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mpirun -n 4 hostname 
, the output is printed correctly. I also checked the version of mpi4py as Cobaya documentation suggests as

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mpirun -n 2 python -c "from mpi4py import MPI, __version__; print(__version__ if MPI.COMM_WORLD.Get_rank() else '')"
and it is 3.1.3 version. So, I am not sure if my mpirun is the problem, I am out of ideas.

Please, could anyone help me on how to solve that issue? I really need to use Cobaya with MPI.

Regards,
Karim

Antony Lewis
Posts: 1812
Joined: September 23 2004
Affiliation: University of Sussex
Contact:

### Re: Cobaya error MPI disabled

Note sure. Check COBAYA_NOMPI env variable is not set. MPI being disabled should only be because either that is set or MPI cannot be imported from mpi4py.

Juan Cruz
Posts: 5
Joined: January 24 2022
Affiliation: University of Southern Denmark - SDU

### Re: Cobaya error MPI disabled

I was also having similar issues. Make sure there is only one openmp and that it is properly linked. You probably have different installations, one from your linux package manager and one from anaconda. I would say option one, try to create a clean new environment in conda and at creation include openmp and mpi4py so that conda does the correct linking. Option 2 create a new invironment without openmp or mpi4py and use pip (of the new enviroment) afterwards to install mpi4py, this should link to the openmp from the linux package manager. Hopefully this solves the issue.

Obs: Also your logs seem to say python 3.9 not 3.8 and you seem to have installed cobaya using the "--user" which makes things go to .local, for easy access and cleanliness when using conda environments avoid using --user so that the environment remains self-contained. (my opinion)