Evaluation of UFL expression at mesh points

dokken · December 23, 2021, 5:10pm

You can use dolfinx.Expression as shown in

FEniCS/dolfinx/blob/114c268aab752b6669abc2718837116cec90dba6/python/test/unit/fem/test_expression.py#L70

    
      
          cell_geometry = np.zeros((num_dofs_x, gdim), dtype=np.float64)
          points_ref = np.zeros((len(local_map), tdim))
          
          
# Map cells on process back to reference element
          for i, cell in enumerate(closest_cell):
              cell_geometry[:] = x[x_dofs[cell], :gdim]
              point_ref = mesh.geometry.cmap.pull_back(points[local_map[i]][:gdim].reshape(1, -1), cell_geometry)
              points_ref[i] = point_ref
          
          
# Eval using Expression
          expr = Expression(grad_u, points_ref)
          grad_u_at_x = expr.eval(closest_cell).reshape(len(closest_cell), points_ref.shape[0], gdim)
          
          
# Compare solutions
          for i, cell in enumerate(closest_cell):
              point = points[local_map[i]]
              assert np.allclose(grad_u_at_x[i, i], gradf(point))

Some nicer front-end UI will hopefully be merged soon with: Interpolation of ufl expressions by jorgensd · Pull Request #1875 · FEniCS/dolfinx · GitHub

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Evaluation of UFL expression at mesh points

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