[petsc-users] Hash Function for PETSc Sparse Matrices

[K. N. Ramachandran]

Hello Jed, Barry,

Thanks for the inputs. Yes, I am trying to spot duplicate sparse Matrices
basically and avoid storing if possible. MatGetNonzeroState() seems useful
here and I'll take a closer look.

I couldn't find the PetscObjectGetState() though from the available API (
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/singleindex.html).
Was there another closely related function I should take a look at?

Thanks,
Ram



On Mon, Dec 5, 2016 at 9:26 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Dec 5, 2016, at 2:47 PM, K. N. Ramachandran <knram06 at gmail.com>
> wrote:
> >
> > Hello PETSc-Users,
> >
> > I am working on an application where we capture the A matrix in a linear
> system Ax=b, which is solved using Petsc. Let us also say that the matrix A
> can change after a few iterations. We want to capture only the changed
> matrices and simply avoid the duplicate ones.
> >
> > I was considering using (or defining) a Set-like data structure that
> stores only the Mat objects which have changed entries. So a hash function
> that can operate on a sparse matrix would be pretty useful here.
> >
> > This seems like a common enough use case and I was wondering if anyone
> can give their inputs on defining a hash function that can operate on
> sparse matrices. One such link I had found online is:
> > http://stackoverflow.com/questions/10638373/suitable-
> hash-function-for-matrix-sparsity-pattern
> >
> > Any thoughts or comments would be great here.
>
> PETSc automatically tracks changes in the numerical values and sparsity
> pattern of its matrices. So, for example, if you call MatSetValues() and
> MatAssemblyBegin/End() then the KSP associated with the Mat "knows" the
> matrix has changed. Similarly if the sparsity pattern changes then
> preconditioners that depend on the sparsity pattern, such as ILU, take the
> change into account when they rebuild the preconditioner. You can inquire a
> PETSc matrix for its current state or nonzero pattern state and compare
> with saved previous state to see if it has changed us PetscObjectGetState()
> for numerical changes and MatGetNonzeroState() for nonzero structure
> changes.
>
> I don't know if this is related to your inquiry or not.
>
>   Barry
>
> >
> >
> > Thanking You,
> > Ramachandran
>
>


-- 
K.N.Ramachandran
Ph: 814-441-4279
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20161206/f8879a63/attachment.html>