Matrix Allocation

[Matthew Knepley]

  1) Could you be calling MatGetInfo() with the wrong matrix?

  2) Can you use -info to check the numbers?

  3) Can you try MatSetOption(A, MAT_NEW_NONZERO_ALLOCATION_ERR, 1)?

     Matt

On Mon, Jun 30, 2008 at 12:25 PM, Andrew Colombi <acolombi at gmail.com> wrote:
> I am a little confused by some behavior.
>
> I've been trying to understand some poor performance numbers and I
> noticed that if I doubled the preallocation numbers (presently I'm
> setting d_nz and o_nz to constants, no effort has been made to get the
> numbers _right_) performance improved dramatically (about 20X).
>
> This isn't so surprising except for the report from MatGetInfo.  Even
> with the lower preallocation numbers I'm getting 0 in info.mallocs for
>
> MatInfo info;
> MatGetInfo(pc_A, MAT_LOCAL, &info); // done and reported on each
> machine individually
>
> So, my question is.... well.. why?  If I'm seeing 0 mallocs before
> doubling prealloation shouldn't that mean I've preallocated enough?
> Or are their some switches I need to use to enable malloc counting?
> Also you can see (according to the same call to MetGetInfo) I'm
> wasting a lot of memory:
>
> // after doubling preallocation
> nz_alloc 6.2704e+07 nz_used 1.9125e+07 nz_unneed 4.3579e+07
>
> (these are print outs of info.nz_allocated, info.nz_used and info.nzunneeded).
>
> Any thoughts?  For now memory is not a bottleneck, so I guess I'll be
> satisfied with guessing big numbers for d_nz and o_nz.  Still, I spent
> a lot of time scratching my head since guessing higher numbers didn't
> seem likely to have an effect.
>
> Thanks,
> -Andrew
-- 
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