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

Arthur Kurlej akurlej at gmail.com
Wed Jun 25 15:10:37 CDT 2014

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
-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?

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