GMRES Tutorial

[ajnonaka]

Simple driver and class for unpreconditioned GMRES for Poisson equation.

[ajnonaka]

I think I need to change the initial condition to be random (and sum to zero) - it's converging too easily with sin(2 pi x) on the RHS.

[WeiqunZhang]

I think I have got precon working. Do you want me to push the changes?

[ajnonaka]

Sure I was going to ask you about it later today but go ahead and push and I'll study the differences. Thanks!

[WeiqunZhang]

Maybe we can add some comments to what the preconditioner is supposed to do. It is supposed to solve P(lhs) = rhs, where P is an approximation for A. In the case that no preconditioner is used, P is an identity matrix.

[ajnonaka]

yes both in this PR and in the amrex/src... I was going to pull the comments from the classes in there directly into this PR.

[WeiqunZhang]

It might also be worth mentioning here and in amrex/Src that we use right preconditioning.

[ajnonaka]

I'll do a little tidying and merge (later today)

[ajnonaka]

And I'll update the documentation.