[petsc-dev] CheckPointer

[Dave May]

Hey Jed,

The overhead is big.
Here are some numbers I generated which prompted Matt's email.

All the total run times reported are almost entirely associated with matrix
assembly.
All builds used --with-debugging=yes

Time (sec):           6.285e+00 [petsc v3.2]
Time (sec):           1.966e+02 [petsc v3.4]
Time (sec):           8.960e+00 [petsc v3.4 with a hacked checkptr.c which
skips the checking]

Calls to MatSetValue  5955066
Calls to MatSetValues 11910132

[0] MatAssemblyEnd_SeqAIJ(): Matrix size: 13473 X 13473; storage space: 0
unneeded,1359333 used
[0] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0
[0] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 226

Cheers,
  Dave


On 11 September 2013 15:51, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> What about a run-time option to enable it?
>
> What is the actual overhead for an application that calls MatSetValues
> with fine granularity?
> On Sep 11, 2013 6:13 AM, "Matthew Knepley" <knepley at gmail.com> wrote:
>
>> The new CheckPointer() is 1000s of times slower than the previous. We may
>> want to have a configure option to disable it.
>>
>> I am not convinced, since the only function that it really matters for is
>> MatSetValues(), which is a problematic interface function.
>>
>>    Matt
>>
>> --
>> 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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