Running ORCA in parallel with CHEMSHELL mpi version

Dear Developers,

I intend to use DL-FIND for my QM/MM optimization and plan to utilize task farming parallelism. However, my HPC environment does not allow ORCA to call mpirun while CHEMSHELL itself launches the mpirun binary. How should I go about this? Is it possible to run both in parallel?

Thank you


There’s no easy solution to this at the moment unfortunately as ORCA is made available only as a binary distribution, and so it’s not possible for its MPI environment to be shared with ChemShell via direct linking as a library, which is the usual way to enable task-farming parallelisation with ChemShell.

If you’re certain it’s not possible for mpirun to be called from a program that has itself been launched with mpirun on your platform, and you still want to use task-farming, then the best bet might be to switch to a QM code which can be directly linked to ChemShell, at least for the optimisation. Otherwise it may be possible to hack a solution, e.g. by compiling ChemShell with Intel MPI while running ORCA with OpenMPI.

Best wishes,


Dear Tom,

Thank you for your prompt response. I will proceed with compiling CHESHELL using Intel MPI and running ORCA with Open MPI to determine if this resolves the issue.

Best regards,