[petsc-users] How to symmetrical the pattern of anunsymmetrical matrix

[Gong Ding]

> 2011/1/26 Gong Ding <gdiso at ustc.edu>
> 
>> I have unsymmetrical jacobian matrix in MPIAIJ format (it is nearlly
>> symmetric, I guess). I'd like to pad it to symmetrical pattern by just add 0
>> to corresponding matrix entry, which is required to some matrix partition
>> step.
 
 
> How are you obtaining the matrix?  The best way is to preallocate those
> extra zeros.
Yes, it is the problem. I have to build the pattern of symmetrical  matrix for memory allocation from the unsymmetrical matrix.
I don't konw how to do it with petsc API.  Any good idea?
After build the symmetrical  matrix, things are easy.


> A traditional purely algebraic way is to add the transpose (zeroed in this
> case), but transpose is a bad operation to perform in parallel so I would
> try to avoid it.