[petsc-users] Reading in the full matrix in one process and then trying to solve in parallel with PETSc

[Bao Kai]

Thanks a lot, Matt.

I will do that.

Cheers,
Kai

On Fri, Sep 20, 2019 at 2:08 PM Matthew Knepley <knepley at gmail.com> wrote:
>
> On Fri, Sep 20, 2019 at 7:54 AM Bao Kai via petsc-users <petsc-users at mcs.anl.gov> wrote:
>>
>> Hi,
>>
>> I understand that PETSc is not designed to be used this way, while I
>> am wondering if someone have done something similar to this.
>>
>> We have the full matrix from a simulation and rhs vector. We would
>> like to read in through PETSc in one process, then we use some
>> partition functions to partition the matrix.
>>
>> Based on the partition information, we redistribute the matrix among
>> the processes. Then we solve it in parallel.  It is for testing the
>> performance of some parallel linear solver and preconditions.
>>
>> We are not in the position to develop a full parallel implementation
>> of the simulator yet.
>
>
> This is not hard to do.
>
> 1) Write a simple serial converter that reads in your matrix in whatever format you have it, and output it in PETSc Binary format
>      using MatView() with a binary viewer. Same for the vector, and they can be in the same file.
>
> 2) Run your parallel code and use MatLoad/VecLoad for the system and it will automatically partition it.
>
>   Thanks,
>
>      Matt
>
>>
>> Thanks.
>>
>> Cheers,
>> Kai Bao
>
>
>
> --
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
>
> https://www.cse.buffalo.edu/~knepley/