GMRES Driver Improvements

[patrikrac]

GMRES Driver Improvements

The current GMRES driver was left-preconditioned only and its stopping criterium was based on the preconditioned relative residual (standard for left preconditioned Krylov methods).

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The update delivers following improvements aiming at improving robustness and reducing iteration counts in a variety of simulations:

• Fixed a bug in the Gram-Schmidt orthogonalization loops which could cause unnecessary iterations.
• Added switch for right preconditioning -> Default set to right in since we can capture the true residual.
• Added a breakdown guard that allows for "happy" breakdown of the Krylov subspace and thus early exiting.
• Added right hand side normalized stopping criterion which better accounts for good initial guesses.

[N-Schwarz]

Hi @patrikrac , what is the status on this?

[patrikrac]

Hi @N-Schwarz, I didn't get around to rerunning the regression tests yet. I will start them now since I am back from holidays. I imagine though i will probably still run into issues with the stellerator cases, or is this fixed now?
From a code side this should be final.