Calling mpirun from bash file does not recognize $VAR format...?

Question

While trying to run the following .sh file I get an error from mpirun:

The file: (additional python config omitted for brevity)

NB_MPI_WORKERS=2
SEED=0

mpirun --n ${NB_MPI_WORKERS} python start.py --base_path ~/temp --seed ${SEED}

The error:

Open MPI has detected that a parameter given to a command line
option does not match the expected format:

  Option: n
  Param:  2

This is frequently caused by omitting to provide the parameter
to an option that requires one. Please check the command line and try again.

I have confirmed that simply replacing ${NB_MPI_WORKERS} with 2 does work, so I'm a bit confused on where the error is, especially since ${seed} is working.

Can anyone clarify, please? Is it actually an issue of formatting, or maybe type?

Versions:

• Linux Mint 20.2
• Open MPI 4.1.2

Answer 1

As suggested in the comments, the solution was to convert the file from DOS text file format to Unix text file format to replace the line endings.

Since the file was in DOS text format, the trailing carriage-return character got added onto the values of both NB_MPI_WORKERS and SEED. In the case of SEED, it didn't seem to be a problem as the value was somehow properly handled by the Python script. But in the case of the other variable, it meant the --n option got a value that was not recognized as legal.