# [petsc-users] I am wondering if there is a way to implement SPMM

Cong Li solvercorleone at gmail.com
Tue Aug 4 04:09:30 CDT 2015

```I am sorry that I should have explained it more clearly.
Actually I want to compute a recurrence.

Like, I want to firstly compute A*X1=B1, and then calculate A*B1=B2,
A*B2=B3 and so on.
Finally I want to combine all these results into a bigger matrix C=[B1,B2
...]

Is there any way to do this efficiently.

On Tue, Aug 4, 2015 at 5:45 PM, Patrick Sanan <patrick.sanan at gmail.com>
wrote:

> On Tue, Aug 04, 2015 at 03:42:14PM +0900, Cong Li wrote:
> >
> > I have an other question.
> > I want to do SPMM several times and combine result matrices into one
> bigger
> > matrix.
> > for example
> > I firstly calculate AX1=B1, AX2=B2 ...
> > then I want to combine B1, B2.. to get a C, where C=[B1,B2...]
> >
> > Could you please suggest a way of how to do this.
> This is just linear algebra, nothing to do with PETSc specifically.
> A * [X1, X2, ... ] = [AX1, AX2, ...]
> >
> > Thanks
> >
> > Cong Li
> >
> > On Tue, Aug 4, 2015 at 3:27 PM, Jed Brown <jed at jedbrown.org> wrote:
> >
> > > Cong Li <solvercorleone at gmail.com> writes:
> > >
> > > > Hello,
> > > >
> > > > I am a PhD student using PETsc for my research.
> > > > I am wondering if there is a way to implement SPMM (Sparse
> matrix-matrix
> > > > multiplication) by using PETSc.
> > >
> > >
> > >
> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatMatMult.html
> > >
>
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