[petsc-users] Insert one sparse matrix as a block in another

[Jed Brown]

The description matches MATNEST (MATCOMPOSITE is for a sum or product of matrices) or parallel decompositions. Also consider the assembly style of src/snes/tutorials/ex28.c, which can create either a monolithic or block (MATNEST) matrix without extra storage or conversion costs.

Mark Adams <mfadams at lbl.gov> writes:

> Do you know what kind of solver works well for this problem?
>
> You probably want to figure that out first and not worry about efficiency.
>
> MATCOMPOSITE does what you want but not all solvers will work with it.
>
> Where does this problem come from? We have a lot of experience and might
> know something.
>
> Mark
>
> On Mon, Dec 12, 2022 at 1:33 PM Peder Jørgensgaard Olesen via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
>> Hello
>>
>>
>> I have a set of sparse matrices (A1, A2, ...) , and need to generate a
>> larger matrix B with these as submatrices. I do not know the precise sparse
>> layouts of the A's (only that each row has one or two non-zero values),
>> and extracting *all* values to copy into B seems incredibly wasteful. How
>> can I make use of the sparsity to solve this efficiently?
>>
>>
>> Thanks,
>>
>> Peder
>>
>>
>>
>> Peder Jørgensgaard Olesen
>> PhD student
>> Department of Civil and Mechanical Engineering
>>
>> pjool at mek.dtu.dk
>> Koppels Allé
>> Building 403, room 105
>> 2800 Kgs. Lyngby
>> www.dtu.dk/english
>>
>>