Kokkos, mpirun: Error: unknown option "-ppn"

Hello Lammps users,

Today I compiled lammps with kokkos package with following command

make mpi KOKKOS_DEVICES=OpenMP

But when I tried to use the following command to run the simulation

mpirun -np 32 -ppn 4 lmp_mpi -k on t 4 -sf kk -in in.bn
It shows an error mpirun: Error: unknown option "-ppn"
and when I run without keyword -ppn it shows warnings
WARNING: Fixes cannot send data in Kokkos communication, switching to classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to classic communication (../comm_kokkos.cpp:368)

why this is happening ? is there any problem in installation?

Please suggest.

Thanks

Rajesh

Hello Lammps users,

Today I compiled lammps with kokkos package with following command

make mpi KOKKOS_DEVICES=OpenMP

But when I tried to use the following command to run the simulation

mpirun -np 32 -ppn 4 lmp_mpi -k on t 4 -sf kk -in in.bn

It shows an error mpirun: Error: unknown option "-ppn"

-ppn is a flag specific to the mpirun command from MPICH (and derived
MPI libraries). you obviously are using a different MPI library with
different command line flags.

and when I run without keyword -ppn it shows warnings

WARNING: Fixes cannot send data in Kokkos communication, switching to
classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to
classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to
classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to
classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to
classic communication (../comm_kokkos.cpp:368)
WARNING: Fixes cannot send data in Kokkos communication, switching to
classic communication (../comm_kokkos.cpp:368)

why this is happening ? is there any problem in installation?

there are two "problems" visible here:

1) you get this output multiple times. that means, your mpirun command
does not match the MPI library, you compile LAMMPS with. that is a
serious problem (but has nothing to do with KOKKOS), but is a user
problem.

2) the warning itself is triggered when using a fix that stores per
atom data. in that case, communication between MPI ranks has to be
done with the non-KOKKOS aware Comm class, which in turn requires,
that all KOKKOS specific optimized data storage will have to be
synchronized with the "conventional" storage first. this is not really
a problem, but just a warning to alert you of the additional overhead
that can be incurred this way.

axel.