On Nov 29, 2009, at 9:21 PM, ming zhu wrote:
> OK.
> may I ask , I think Petsc matrix is row -based. That means,
> MatGetArray(Mat mat,PetscScalar *v[])
> v[0] is the pointer to the first row. v[0][0] is the value of mat[0]
> [0].
> Am I right?
No. It is column based and there is just one array for the who
thing so v[0:m-1] is the first column v[m:2m-1] is the next column etc
> And do you mean that, each time I got a vector, I create a sub
> matrix to store it.
No. Just create the full matrix and copy over each vector as you get
it.
Barry
> Later on, the merging will be a problem.
>
> --- 09?11?30????, Barry Smith <bsmith at mcs.anl.gov> ?
> ??
>
> ???: Barry Smith <bsmith at mcs.anl.gov>
> ??: Re: How to fill a matrix with a vector parallelly
> ???: "PETSc users list" <petsc-users at mcs.anl.gov>
> ??: 2009?11?30?,??,??11:12
>
>
> On Nov 29, 2009, at 9:09 PM, ming zhu wrote:
>
> > Thank you for your quick reply.
> > Two questions:
> > one, how do I know which part belongs to the present processor?
>
> Call VecGetOwnershipRange() to know what rows of the vector belong
> to the process. Then create the MPIDense matrix with the same number
> of local rows.
>
> > second, is there any examples for this kind of question?
> >
> > Thank you
> >
> > --- 09?11?30????, Barry Smith <bsmith at mcs.anl.gov> ?
> ??
> >
> > ???: Barry Smith <bsmith at mcs.anl.gov>
> > ??: Re: How to fill a matrix with a vector parallelly
> > ???: "PETSc users list" <petsc-users at mcs.anl.gov>
> > ??: 2009?11?30?,??,??9:53
> >
> >
> > Since evenvectors will (almost always) be dense vectors you will
> want to use a MPIDENSE matrix to store them. So create a MPIDENSE
> matrix with the same row layout as the eigenvector then on each
> process use VecGetArray() to access that processes part of the
> vector and MatGetArray() to access that part of the matrix and copy
> the values over from the vector array to the matrix array.
> >
> > Barry
> >
> > On Nov 29, 2009, at 7:41 PM, ming zhu wrote:
> >
> > > HI
> > > I am trying to solve an eigenvalue problem. A = U * LAMBDA*U'.
> While SLEPC proivdes a solver to get an eigenvector and the related
> eigenvalue, I have to fill the eigenvector to form the eigen matrix.
> However, there seems no such function to do this directly. I was
> trying to use VecGetValues and filled the matrix one by one.
> Howevevr, it can not do that in parallel.
> > >
> > > Is there anyone can help me ?
> > >
> > > Thank you
> > >
> > >
> > > ?????????????????
> >
> >
> > ?????????????????
>
>
> ?????????????????
