Hi all, I have an assembled matrix with zero rows, where I’d like to insert ones on the diagonal. In older versions there was the A.ident_zeros() function which did exactly that, and fast. Such a function seems not to be implemented in dolfinx, so I tried to find a workaround with PETSc, using: A…

I would suggest the following: import time import dolfinx import numpy as np import ufl from dolfinx import cpp, fem from mpi4py import MPI from petsc4py import PETSc N = 75 degree = 1 mesh = dolfinx.mesh.create_unit_cube(MPI.COMM_WORLD, N, N, N) V = dolfinx.fem.FunctionSpace(mesh, ("CG", degree)…

Great, thank you! Very neat approach. Just one thing, running your example in parallel gives an error in np.delete(all_blocks, boundary_blocks), since the indices in boundary_blocks exceed the size of all_blocks. @CastriMik this looks identical to what I did in the setDiagonal() variant, doesn’t it…

Yes, sorry for that (I completely missed that function).

[image] dokken: all_blocks = np.arange(imap.size_local, dtype=np.int32) Just change this to all_blocks = np.arange(imap.size_local+imap.num_ghosts, dtype=np.int32)

Modify matrix diagonal -- dolfinx version for A.ident_zeros()

General

CastriMik December 7, 2022, 1:46pm 2

You can find a version of ident_zeros() for DOLFINx in this post.

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Modify matrix diagonal -- dolfinx version for A.ident_zeros()

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