[petsc-users] SetVariableBounds vs ComputeVariableBounds

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:

>    There is the same issue with ODE integrators for linear problems. The solvers tromp on the Jacobian.  

So with TS, the shift comes from a mass matrix and that matrix could
conceivably change independent of whether the (RHS) Jacobian has
changed.

>    We should actually add an error indicator in these TAO/TS solvers, if the "Jacobian" state value is not increased in the next time step/iteration this means the person did not supply the new Jacobian (in other words the Jacobian is still whatever it was tromped to) so the solver should error out and tell the user their mistake.

But with TAO, isn't the shift always diagonal?  It seems wasteful to
always do a full assembly (or store a pristine copy) when only a
modified shift is needed.  If there is a simple and reliable way to
correct the shift, it would be a nicer interface to just do the right
thing.  Note that TS is extra confusing because the user can pass
IJacobian, RHSJacobian, or both, and we reuse whichever matrix they
provide.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 818 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20160628/cfb85dd9/attachment.pgp>