Leo/cross mesh non lagrange #4804
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pbrubeck
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Jan 21, 2026
firedrake/interpolation.py
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| point_eval, point_eval_input_ordering = self._get_symbolic_expressions() | ||
| # Interpolate into intermediate quadrature space for non-identity mapped elements | ||
| if into_quadrature_space := V_dest.ufl_element().mapping() != "identity": |
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Careful here with symmetric TensorElements
pbrubeck
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Jan 22, 2026
| weights = numpy.full(len(points.points), numpy.nan) # These can be any number since we never integrate | ||
| quad_scheme = QuadratureRule(points, weights, ref_el=V_element.cell) | ||
| element = FiniteElement("Quadrature", degree=V_element.degree, quad_scheme=quad_scheme) | ||
| return self._fs_type(V)(V.mesh(), element) |
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The Quadrature space is always scalar-valued, even if it came from a vector-valued space like RT. You should grab the value_shape, and not the Tensorness of the ufl element.
This should be generic enough, although it might be better to special case the scalar case
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| return self._fs_type(V)(V.mesh(), element) | |
| return TensorFunctionSpace(V.mesh(), "Quadrature", degree=V_element.degree, quad_scheme=quad_scheme, shape=V.value_shape) |
pbrubeck
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Jan 22, 2026
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| "Can't yet cross-mesh interpolate onto function spaces made from VectorElements " | ||
| "or TensorElements made from sub elements with value shape other than ()." |
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This should no longer be the case after this PR
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Implement cross-mesh interpolate into non-point evaluation spaces.
To do this we first construct a quadrature space which has point-evaluation dofs at the quadrature points of the target element. We then cross-mesh interpolate into this space. Finally, we interpolate from this quadrature space into the target space.