[petsc-users] Appending to vector / numerical continuation / slepc

[Kevin Green]

Jose - Thank you, I'll see if I can get this working.

Barry - This seems to be exactly what I'm looking for.  Glancing at the
documentation briefly, some questions do spring to mind, but I will not ask
until I look at some of the examples!

Mike - Thanks for the updated link, I didn't even notice that Barry's was
for 3.0.0.

In the meantime, I'll update to petsc 3.2, and slepc-dev, and get looking at
these examples.  This isn't at the immediate top of my todo list, but I
expect I'll have some detailed questions  on DMCOMPOSITE in a week or so.

Kevin



On Wed, Oct 5, 2011 at 5:35 PM, Mike McCourt <mccomic at mcs.anl.gov> wrote:

> If you're gonna use PETSc 3.2, make sure to check out the updated
> documentation:
>
>
> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/DM/DMCompositeCreate.html
>
> It has a more accurate list of examples.
>
> -Mike
>
> ----- Original Message -----
> From: "Barry Smith" <bsmith at mcs.anl.gov>
> To: "PETSc users list" <petsc-users at mcs.anl.gov>
> Sent: Wednesday, October 5, 2011 4:29:14 PM
> Subject: Re: [petsc-users] Appending to vector / numerical continuation /
>     slepc
>
>
>  Kevin,
>
>    The DMCOMPOSITE is designed exactly for this purpose. See the manual
> page
> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-3.0.0/docs/manualpages/DA/DMCompositeCreate.html#DMCompositeCreateand examples it links to. Essentially you create a DMCOMPOSITE and then use
> DMCompositeAddDM() to put in the DM which will be parallel and
> DMCompositeAddArray() for the "k" extra things (like continuation
> parameters).   After you read the manual pages and look at the examples and
> start your code using the DMCOMPOSITE, feel free to ask specific questions
> about its usage.
>
>   You definitely should switch to PETSc 3.2 before working because the DM
> has been markedly improved in places for this type of thing,
>
>   Barry
>
>
>
> On Oct 5, 2011, at 12:46 PM, Kevin Green wrote:
>
> > Greetings,
> >
> > I was just wondering what the simplest way to create a new N+k dim where
> the first N come from a DA.  It seems to me that I would have to go the
> round about way of getting the array, then writing that to the first N
> components of the new vector... I think there would be a bit of a pain for
> the parallel case when doing this though, like in managing the change in the
> local sizes when going from N to N+k... perhaps it's not that tricky.  Also,
> with DAs I don't have to worry about orderings, correct?
> >
> > Essentially I want to get pseudo-arclength continuation working using the
> SNES solver.  Another option I'm thinking is that rather than using an
> extended vector, I could use a MatShell where the added components are
> located within its context, and updated upon matmult...since k is typically
> small, this seems reasonable.  Do you know of any code/projects that make
> use of the SNES module for continuation?  Any thoughts on what would be the
> better or simpler way of doing this?
> >
> > I'm using petsc-3.1 right now, as I also need slepc...which hasn't been
> updated to work with 3.2 yet, as far as I know.  I'm fairly new to
> petsc/slepc... so I have to ask, what is the timescale like between the
> release of a new petsc, and update of slepc?  Or is there a way to get slepc
> working with the new release?
> >
> > Cheers,
> > Kevin
>
>
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