[petsc-users] Change the matrix row order

[我]

Thanks for your reply! And sorry for my late answer. I want to parallel a particle-method code and solve Ax=b in each timestep.  In this code, each partition forms a CSR matrix and assembles the final coefficient matrix by MatCreateMPIAIJWithArrays. But, the domain decomposition makes that the particles' order doesn't follow the original order. In other words, Solution Vector x follows the original order but Vector b follows a new order due to domain decomposition. So I want to change the Vector b's order and Matrix A's row order to follow the origin order. I have been considering to change my parallel code in these days, but I didn't find a best way. I'm considering to multiply a renumbering identity matrix at both sides of the equation with function MatMatMult. Do you have any suggestions for this problem? If the function MatMatMult can influence the parallel efficiency obviously?

Thanks again!
Daye






At 2018-04-10 22:07:04, "Smith, Barry F." <bsmith at mcs.anl.gov> wrote:
>
>   When and where do you want to change the row order?
>
>   For PETSc and external factorization based solvers this is handled automatically, no need to do anything.
>
>   The ordering of matrix rows corresponds to the ordering of the vectors; almost always one partitions and orders the vectors based on the mesh that underlies the problem and there is no reason to reorder once the layout is initially determined.
>
>   Barry
>
>
>
>> On Apr 10, 2018, at 8:42 AM, 我 <dayedut123 at 163.com> wrote:
>> 
>> Hello,
>> I want to change the row order of a sparse matrix. Are there any build-in functions and suggestions?
>> Thank you very much!
>> Daye
>> 
>> 
>>  
>
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