about MatSetValues()

Hong Zhang hzhang at mcs.anl.gov
Wed Oct 18 09:22:58 CDT 2006


> In this function I need to provide the number of rows and their global indices and
>the number of columns and their global indices.
>What I want to know is if I only give these
>indices regardless which porcessor ownes its indices?

Yes. User does not need to know the ownership of rows/columns.
Petsc hides low-level communications to enable fast
code development. When user knows the distribution
of data, he is able to set values into the owned processor
for better performance. Take a look at the petsc tutorial sliedes posted
We have detailed introduction on this subject.

>In another words,
>do I need to know the indices,
which this process ownes before I call this function?
You don't have to know. But if you know, you
can write a better application code.


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