Radiation Transport Working

The Implicit radiation transport solver is working in parallel for fixed grid.

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It takes hypre a long time to converge initially. I'm assuming this is because the opacity is so low yet the radiation field is very far out of equilibrium.

So after some investigation it looks like the matrix tends to be very ill conditioned (condition numbers of 1e9).

The solution is to start with a small time step and change the cfl relaxation parameter to be ~ 1e-3… If the hydro time step (or the radiative cooling time step) is ~10 orders of magnitude longer than the diffusion time scale - and the system is not in thermal equilibrium - then the matrix becomes too ill-conditioned for hypre to solve.

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