topic Re: Do all dependences need to compiled using MPI if the main program needs MPI compilation? in Intel® Fortran Compiler

Do all dependences need to compiled using MPI if the main program needs MPI compilation?

efnacy — Fri, 21 Aug 2020 00:47:04 GMT

I have a program that needs to be compiled with MPI parallelization, say I am using openmpi installed using intel compilers and this program depends on external libraries. Following the recommendation that dependencies and main programs should be compiled by the same compiler and same flags, do I then also need to compile the dependencies of my program using MPI wrappers even if their code is only serial or is it sufficient to use the underlying compiler of my openmpi (in this case the intel compilers)?

Re: Do all dependences need to compiled using MPI if the main program needs MPI compilation?

Arjen_Markus — Tue, 25 Aug 2020 07:42:07 GMT

As MPI is a pure library, not a library and a set of compiler directives like OpenMP (no "I"), I would say that it is not necessary to recompile the external libraries, as long as they are compiled with the same compiler. What will be important is to use the same MPI environment, so in this case OpenMPI. Other MPI environments are not compatible, if I understand it correctly.

Re: Do all dependences need to compiled using MPI if the main program needs MPI compilation?

efnacy — Sat, 29 Aug 2020 22:52:33 GMT

You mean, only openMPI is compatible with openMP? I thought openMP and openMPI are unrelated, they just happened to have similar name. This means that if I want to combine MPI and shared-memory parallelization using openMP, my only choice for the MPI implementation would be openMPI?

Re: Do all dependences need to compiled using MPI if the main program needs MPI compilation?

Steve_Lionel — Sat, 29 Aug 2020 23:06:26 GMT

They are unrelated other than by the name similarity.

Re: Do all dependences need to compiled using MPI if the main program needs MPI compilation?

JohnNichols — Sun, 30 Aug 2020 18:27:02 GMT

Excuse humour:

Brad Pitt and I have the opposite problem.

Re: Do all dependences need to compiled using MPI if the main program needs MPI compilation?

Ron_Green — Mon, 31 Aug 2020 14:12:42 GMT

External objects and libraries: as long as they make no MPI calls and are compiled with the same compiler major version: these do not have to be recompiled with the MPI wrappers.

Re: Do all dependences need to compiled using MPI if the main program needs MPI compilation?

Barbara_P_Intel — Mon, 31 Aug 2020 16:37:19 GMT

And be sure to link with the MPI driver, mpifort, to include the MPI libraries.