[petsc-users] Question-Memory of matsetvalue

[Jed Brown]

This is what I'd expect to observe if you didn't preallocate correctly for the second matrix, which has more nonzeros per row.

https://petsc.org/release/docs/manual/mat/#sec-matsparse

김성익 <ksi2443 at gmail.com> writes:

> Hello,
>
>
>
> I have a question about memory of matsetvalue.
>
> When I assembly the local matrix to global matrix, I’m just using
> matsetvalue.
> Because the connectivity is so complex I can’t use matsetvalues.
>
> I asked this question because I was curious about how ram memory is
> allocated differently for the two simtuations below.
>
>
>
> First situation.
>
> The local matrix size is 24 by 24. And the number of local matrix is
> 125,000.
>
> When assembly procedure by using matsetvalue, memory allocation does not
> increase.
> So I just put Matassemblybegin and matassemblyend after all matsetvalue.
>
>
>
> Second situation.
>
> The local matrix size is 60 by 60. And the number of local matrix is 27,000.
>
> When assembly procedure by using matsetvalue, memory allocation does
> increase.
>
> So I just put Matassemblybegin and matassemblyend after each local matrix
> assembly.
> This did not increase the memory further..
>
>
>
> Why this situation is happen?
>
> And is there any way to prevent the memory allocation from increasing?
>
>
>
>
>
>
>
> Thanks,
>
> Hyung Kim