You can call MatSetOption(mat,MAT_NEW_NONZERO_LOCATION_ERR) then insert the
new values. If it is just a handful of new insertions the extra time should be
small.
Making a copy of the matrix won't give you a new matrix that is any faster
to insert into so best to just use the same matrix.
Barry
> On May 19, 2024, at 7:44 PM, Adrian Croucher <[email protected]>
> wrote:
>
> This Message Is From an External Sender
> This message came from outside your organization.
> hi,
>
> I have a Jacobian matrix created using DMCreateMatrix(). What would be
> the best way to add extra nonzero entries into it?
>
> I'm guessing that DMCreateMatrix() allocates the storage so the nonzero
> structure can't really be easily modified. Would it be a case of
> creating a new matrix, copying the nonzero entries from the original one
> and then adding the extra ones, before calling MatSetUp() or similar? If
> so, how exactly would you copy the nonzero structure from the original
> matrix?
>
> Background: the flow problem I'm solving (on a DMPlex with finite volume
> method) has complex source terms that depend on the solution (e.g.
> pressure), and can also depend on other source terms. A simple example
> is when fluid is extracted from one location, with a pressure-dependent
> flow rate, and some of it is then reinjected in another location. This
> can result in poor nonlinear solver convergence. I think the reason is
> that there are effectively missing Jacobian entries in the row for the
> reinjection cell, which should have an additional dependence on the
> solution in the cell where fluid is extracted.
>
> - Adrian
>
> --
> Dr Adrian Croucher
> Senior Research Fellow
> Department of Engineering Science
> Waipapa Taumata Rau / University of Auckland, New Zealand
> email: [email protected] <mailto:[email protected]>
> tel: +64 (0)9 923 4611
>
>
