Is it possible to create a matrix with linear form

dokken · November 8, 2024, 3:28pm

Then create he mass matrix (using a trial function), and then do MatVec operations internally.
I for instance do this in Python within oasisx:

github.com

ComputationalPhysiology/oasisx/blob/0aabaf188ccd761f8825591a30a3120a66f129fd/demo/assembly_strategies.py#L134


      
          
          # Add convection term
          dolfinx.fem.petsc.assemble_matrix(A, convection_form)
          A.assemble()
          
          # Do mat-vec operations
          with dolfinx.common.Timer(f"~{P} {i} {N} Matvec strategy") as _:
              A.scale(-0.5)
              A.axpy(1.0 / dt, M)
              A.axpy(-0.5 * nu, K)
              A.mult(u_1.x.petsc_vec, b.x.petsc_vec)
              b.x.scatter_forward()
          
          # Compute the vector without using pre-generated matrices
          b_d = dolfinx.fem.Function(V)
          with dolfinx.common.Timer(f"~{P} {i} {N} Action strategy"):
              dolfinx.fem.petsc.assemble_vector(b_d.x.petsc_vec, lhs)
              b_d.x.scatter_reverse(dolfinx.la.InsertMode.add)
              b_d.x.scatter_forward()
          # Compare results
          assert np.allclose(b.x.array, b_d.x.array)

using MatMult — PETSc 3.22.1 documentation

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Is it possible to create a matrix with linear form

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