[petsc-users] [PETSc-Users] The MatSetValues takes too much time

[Mark Adams]

You need to set the preallocation for the matrix.

https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatMPIAIJSetPreallocation.html

On Thu, May 2, 2019 at 7:46 AM Dongyu Liu via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hi,
>
> I am using PETSc sparse matrix ('aij') for a FEM program, when the
> matrix is really big, let's say 1million by 1million, we use setValues
> based on the index vector I and J, but the whole process takes around 2
> hours.
>
> I don't know why it is like that, or is there any option that I should
> set to make this faster?
>
>
> Best,
>
> Dongyu
>
>
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