SIGSEGV fault for large problems

JuliusZ wrote: I can confirm this issue.
I had the same problem and compiling openmpi with gcc 8.3.0 fixed it.

Ok, so the version of C or Fortran compiler used for MUMPS has no effect and it's just the openmpi that has to be compiled with gcc 8.3.0?

well, gcc contains a c (gcc) and fortran (gfortran) compiler. Ideally, everything is compiled with the same version. You can also set this by the environment variables CC, CXX, and FC for cmake.

Yes, you need a new MPI installation. Maybe ask you administrators if they could install it for you.

The MUMPS project does not use cmake. We cannot directly give it the same c/c++/fortran compilers that are used for NGSolve, because it would not find the necessary MPI libraries and flags. Instead, we give it the MPI wrapper-compilers (mpicc, mpicxx, mpifort). When the c/c++/fortran compiler underlying the MPI-wrappers mismatch, you run into problems like yours.

So, when your MPI is compiled with gcc8.3, MUMPS will also be compiled with that version.