[petsc-users] MatMult() returning different values depending on # of processors?

[Barry Smith]

   How different are the values in b? Can you send back a few examples of the different b’s? Any idea of the condition number of C? 

   Barry

On Jun 25, 2014, at 3:10 PM, Arthur Kurlej <akurlej at gmail.com> wrote:

> Hi all,
> 
> While running my code, I have found that MatMult() returns different values depending on the number of processors I use (and there is quite the variance in the values).
> 
> The setup of my code is as follows (I can go into more depth/background if needed):
> -Generate parallel AIJ matrix of size NxN, denoted as A
> -Retrieve parallel AIJ submatrix from the last N-1 rows&columns from A, denoted as C
> -Generate vector of length N-1, denoted as x
> -Find C*x=b
> 
> I have already checked that A, C, and x are all equivalent when ran for any number of processors, it is only the values of vector b that varies.
> 
> Does anyone have an idea about what's going on?
> 
> 
> Thanks,
> Arthur
>