[petsc-users] Modifying the structure of a matrix.

[Shri]

By default, PETSc uses a row distribution with the first m rows on processor 0, next m rows on processor 1, and so on. If the order is not important, then you could remove rows/columns from each processor instead of removing the last n-m rows on the last processor. Thus, the load balance would still be even. Shri ----- Original Message -----
> I'm solving the schrodinger equation in a basis state method and
> looking at adding the azimuthal quantum numbers (the m's) to my basis
> so I can look at circularly polarized light.
> However, when I do this, I'll need to do some sort of convergence
> study to make sure I add enough of them. The way my code is
> structured, it will probably be easier to just remove rows and columns
> from a bigger matrix, instead of adding them to a smaller matrix.
> However, depending on the way I structure the matrix, I could end up
> removing all the values (or a significant portion of them) from a
> processor when I do that.
> Speaking more on that, is the "PETSC_DECIDE" way of finding the local
> distribution smart in any way? or does it just assume an even
> distribution of values? (I assume that it assumes a even distribution
> of values before the assembly, but does it redistribute during
> assembly?)
> Thanks,
> -Andrew
> On May 15, 2012, at 6:40 AM, Jed Brown wrote:
> > On Mon, May 14, 2012 at 10:39 PM, Andrew Spott <
> > andrew.spott at gmail.com > wrote:
> > > That is what I figure.
> > > I'm curious though if you need to manually determine the local row
> > > distribution after you do that. (for example, say you completely
> > > remove all the values from the local range of one processor… that
> > > processor wouldn't be utilized unless you redistribute the matrix)
> > What sizes and method are we talking about? Usually additional
> > (compact) basis functions only make sense to add to one of a small
> > number of processes.
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