[petsc-users] Finite difference approximation of Jacobian

Tang, Qi tangqi at msu.edu
Tue Dec 14 11:34:12 CST 2021

Dear all,

Will someone be able to help with this coloring request on dmstag in the next few weeks? If not, we will try to fix that on our own. We really need this capability for both debugging as well as performance comparison vs analytical Jacobian/preconditioning we implemented. Thanks.


On Dec 13, 2021, at 12:26 PM, Tang, Qi <tangqi at msu.edu<mailto:tangqi at msu.edu>> wrote:

“overallocating” is exactly what we can live on at the moment, as long as it is easier to work with coloring on dmstag.

So it sounds like if we can provide a preallocated matrix with a proper stencil through DMCreateMatrix, then it should work with dmstag and coloring already. Most APIs are already there.


On Dec 13, 2021, at 12:13 PM, Matthew Knepley <knepley at gmail.com<mailto:knepley at gmail.com>> wrote:

Yes, and would not handle higher order stencils.I think the overallocating is livable for the first imeplementation.

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