[petsc-users] RK substeps

[Juha Jäykkä]

> What exactly are you using TAO to do?

I have a large scale minimisation problem related to the problem I am using 
PETSc to solve. The PETSc code is independent, so I could have two PETSc's 
around and use the older one for TAO, but that seems like a lot of hassle 
without significant benefit.

I know the SNES module could be used as a substitute for TAO. At the moment, I 
solve min(\int f(x)), where TAO needs the gradients of f(x); I could also 
solve discrete grad(f(x))=0 with SNES, but as I then need compute the Jacobian 
(=Hessian of f(x)), too, this has seemed to be too memory intensive to be 
useful. I am not aware of a way around this.

-Juha