Store error of iterations of solvers.CG

Main Forum Old-Forum - do not post here
1

Hey,

is there any possibility to store the printed error of the iterations of the solvers.CG solver? I want to make a plot of the error to show different convergence behavior in relation.

Thanks in advance!

2

It is quite an old thread but there are updates on this front, sorry for not answering earlier.
In the current nightly version there is a little rework of the cg solver, you can get it as a basematrix object now and use either its Solve method or do a matrix vector product. You can afterwards get the iteration count and the convergence history:

from ngsolve.krylovspace import CGSolver
solver = CGSolver(a.mat, pre.mat)
u.vec.data = solver * f.vec
print("iteration count =", solver.iterations)
print("convergence history = ", solver.errors)

The design and names might still change, thats why it is not yet exposed to the solvers, but if you want to get anything else let us know.
Best
Christopher

3

Thank you, that is great news! For my application this fits perfectly.

4

Hello,

sorry to dig out this old thread but I think it fits here: Is there any way to get the iterations and errors for the GMRes solver?

Thanks for your support!

5

With the current implementation not really, but you could just copy paste the GMRes solver from the krylovspace.py file to your file and add that functionality.

Best Christopher