During the development of simple Stokes and Navier-Stokes solvers using the PETSc interface in FF, I noticed that the suggested combination of GMRES KSP type and LU preconditioner (with MUMPS) utilizes a tremendous amount of memory on not-so-big problems.
This can be seen using the stokes-3d-PETSc.edp example. If I run it using
-global 45 flag, the mesh will have ~350,000 elements, i.e. a DOF of ~1,600,000, but (if I’m right) it requires more than 50 GB of memory to be solved.
Is this a bug? If not, is there not any other suggestion for the KSP and preconditioner of Stokes equation that requires less memory?