[petsc-users] free unused allocated nonzeros after overestimating preallocation

[Matthew Knepley]

On Mon, May 3, 2010 at 8:40 AM, Jed Brown <jed at 59a2.org> wrote:

> On Mon, 3 May 2010 08:20:44 -0500, Matthew Knepley <knepley at gmail.com>
> wrote:
> > MatAssemblyBegin/End() frees the unused memory, so you must be
> > calculating the amount of memory needed incorrectly.
>
> It compacts the values but does not free the extra memory.  It would be
> easy to add a matrix option to allocate new space for the entries and
> column indices, then copy the entries over, but requires too much memory
> to do it by default.
>

Yep, does not free by default, which would mean making a copy.


> MatDuplicate on the other hand only allocates for the used values, but
> copies the "maxnz" field so it will incorrectly report more allocation
> than there really is.


I can fix this.

   Matt


>
> Jed
>



-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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