If you are worried about doing memcmp on the ranges, it should be in the order
of microseconds. few milliseconds with millions of processes.
On Lisandro workstation, it took 600 microseconds comparing two equal sets of
a million of integers.
Since the square case with same row and col layout covers the 90% of the cases
(and memcmp need to sweep the entire ranges),
we can always have an int flag for MPIAIJ and its variants which is set to -1
at creation and set up properly the first time MatZeroRow_MPIAIJ is called.
On Jun 22, 2016, at 8:08 PM, Barry Smith <bsm...@mcs.anl.gov> wrote:
>
>> On Jun 22, 2016, at 1:24 AM, Lisandro Dalcin <dalc...@gmail.com> wrote:
>>
>> On 22 June 2016 at 00:30, Barry Smith <bsm...@mcs.anl.gov> wrote:
>>> Why not just remove the first if test (below) and just have the two
>>> conditions diag != 0.0 and drag == 0.0
>>>
>>> if ((diag != 0.0) && (mat->A->rmap->N == mat->A->cmap->N)) {
>>> ierr = MatZeroRows(mat->A, len, lrows, diag, NULL,
>>> NULL);CHKERRQ(ierr);
>>
>> What about comparing mat->rmap->N and mat->cmap->N, then compare
>> size(mat->rmap->comm) and size(mat->cmap->comm), and finally compare
>> (memcmp) mat->rmap-range and mat->rmap-range? If everything matches,
>> the row&col layout is square, you know that in all processes so no
>> need to do reductions, and then you can take the fast path zeroing
>> rows on the diagonal block mat->A.
>
> By then it is worth the optimization?
>
>>
>>
>> --
>> Lisandro Dalcin
>> ============
>> Research Scientist
>> Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
>> Extreme Computing Research Center (ECRC)
>> King Abdullah University of Science and Technology (KAUST)
>> http://ecrc.kaust.edu.sa/
>>
>> 4700 King Abdullah University of Science and Technology
>> al-Khawarizmi Bldg (Bldg 1), Office # 0109
>> Thuwal 23955-6900, Kingdom of Saudi Arabia
>> http://www.kaust.edu.sa
>>
>> Office Phone: +966 12 808-0459
>
