Use block preconditioner for mixed Poisson problem #3580
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jorgensd
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jorgensd
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jorgensd
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jorgensd
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jorgensd
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jorgensd
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python/demo/demo_mixed-poisson.py
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| # + | ||
| a_p00 = inner(sigma, tau) * dx + inner(div(sigma), div(tau)) * dx | ||
| a_p11 = inner(u, v) * dx |
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Same comment as above wrt. extract_blocks.
If we want to highlight both methods in 1 demo, we could keep this one as is as it is the simplest one.
jorgensd
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jorgensd
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jorgensd
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@garth-wells In general a really nice addition to DOLFINx. I added some thoughts regarding the demo above. |
Co-authored-by: Jørgen Schartum Dokken <[email protected]>
Co-authored-by: Jørgen Schartum Dokken <[email protected]>
Co-authored-by: Jørgen Schartum Dokken <[email protected]>
Co-authored-by: Jørgen Schartum Dokken <[email protected]>
Co-authored-by: Jørgen Schartum Dokken <[email protected]>
… into garth/mixed-poisson-block
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Switch to a diagonal block preconditioner, with Hypre Auxiliary Space (AMS) for the$H({\rm div})$ block. AMS works in this case because the demo is 2D, in which case RT elements are just a rotation of Nedelec elements. If Hypre is not available (not configured with PETSc or running with complex floats, which are not supported by Hypre) use LU for the $H({\rm div})$ block.
For a 3D mixed Poisson demo, we would need to use the Hypre Auxiliary-space Divergence Solver (ADS) in place of AMS. This requires the 'discrete curl' operator (see #3587).
This change fixes issues with some LU solvers and saddle point problems.
ZeroBaseFormfrom UFL for theemptyblock on the formL(see https://github.com/FEniCS/ufl/blob/eabdb001d648ae02fb2e04890899501ca471d528/ufl/form.py#L836).