[petsc-users] Is there something to be paid attention to about MatIsSymmetric?

[w_ang_temp]

>At 2012-12-02 23:10:51,"Jed Brown" <jedbrown at mcs.anl.gov> wrote:
>The test for symmetry is not implemented for all matrix types. Looking at the code, it seems to only be SeqAIJ, but MatIsTranspose(A,A,...) would also work >for MPIAIJ.
 
 
I made a test. I get all the elements of the matrix and compare the element A(i,j) with
A(j,i). The result shows that the matrix is symmetric. But the result of MatIsTranspose(A,A,0.0,matsysflg,ierr)
shows that it is unsymmetric(matsysflg=0). I think there is something that I donot know about using the function.
 
 



>>On Sun, Dec 2, 2012 at 8:45 AM, w_ang_temp <w_ang_temp at 163.com> wrote:


>>Hello,

>>    I use MatIsSymmetric to know if the matrix A is symmetric.

>>According to my model, it should be symmetric due to the theory.

>>But I always get the result 'PetscBool  *flg = 0', although I

>>set 'tol' a large value(0.001).

>>    Because the matrix is of 20000 dimension, I can not output the

>>matrix to the txt. So I want to konw if there is something to be paid attention to

>>about the function 'MatIsSymmetric' in version 3.2. Or do I have some other ways

>>to determine the symmetry.I think symmetry is one of the most important thing

>>in my analysis.

>>    Thanks.

>>                                               Jim





-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130117/b6c9bfb4/attachment.html>