Fix finite relative-residual at 0th iteration - #3713
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Looks OK to me, it's a pretty minor change. |
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Just to give a bit more context: In transient simualtions we sometimes have convergence in zero iterations, leading to:
Whereas in legacy fenics, the same problem yielded:
This is a simple decay problem |
jorgensd
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Apr 28, 2025
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For what it's worth, this is my attempt at fixing the issue described here by @mcjbo
In legacy-fenics, at the 0th Newton iteration of each timestep, the relative residual was
inf. This is no-longer the case in dolfinx and it makes a bunch of our use cases extremely tricky to solve as the step sometimes solves in zero iterations (ie. doesn't solve) when it should.@jorgensd told me the plan was to replace the NewtonSolver altogether but I thought this could be a quick fix in the meantime