PETSc matrix-matrix multiplication got signal number 11 error in parallel

[chenyongxin]

To answer my own question:

@chenyongxin

As = assemble_matrix(fem.form(ufl.inner(us, vs) * ufl.dx))

The above return value PETSc.Mat As is not finalized as stated:

FEniCS/dolfinx/blob/6189a7e2f42a63cc2bafd10696862efb41f0c3f9/python/dolfinx/fem/assemble.py#L221C1-L252C8

To make it completed, it should be followed by

As.assemble()

N.B. For a assembled vector (PETSc.Vec), its ghost info in parallell should be specified with

bs = assemble_vector(L)
b.ghostUpdate(...)

See

Parallel Sparse PETSc Matrix Generation with dofs as rows and columns

The key here is that you are only access local (owned) indices of the vector (when you call get_local(), not the ghosted values. This means that you are ignoring several contributions to your matrix. I do not know of an easy way of getting those ghost values in dolfin, however, here is a code that does the same thing for dolfinx. from petsc4py import PETSc from mpi4py import MPI import dolfinx import dolfinx.geometry import basix import numpy as np import ufl el = 30 mesh = dolfinx.UnitInterv…