mpirun: Unrecognized argument mca

Question

I have a c++ solver which I need to run in parallel using the following command:

nohup mpirun -np 16 ./my_exec > log.txt &

This command

Answer 1

[mpiexec@tamnun] match_arg (./utils/args/args.c:194): unrecognized argument mca
[mpiexec@tamnun] HYDU_parse_array (./utils/args/args.c:214): argument matching returned error
[mpiexec@tamnun] parse_args (./ui/mpich/utils.c:2964): error parsing input array
                                  ^^^^^
[mpiexec@tamnun] HYD_uii_mpx_get_parameters (./ui/mpich/utils.c:3238): unable to parse user arguments
                                                  ^^^^^

You are using MPICH in the last case. MPICH is not Open MPI and its process launcher does not recognize the --mca parameter that is specific to Open MPI (MCA stands for Modular Component Architecture - the basic framework that Open MPI is built upon). A typical case of a mix-up of multiple MPI implementations.