[petsc-users] Direct linear solver in Petsc

[Matthew Knepley]

On Fri, Jun 12, 2020 at 12:49 PM Qin Lu via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hello,
>
> I plan to solve a small sparse linear equation system using the direct
> solver, since the number of unknowns is small (less than 1000). Here I got
> a few questions:
>
> 1. Is there a general guide line on the size of the system that direct
> solver is more efficient than iterative solver?
>

I would say at least to 50K unknowns, maybe 100K, depending on sparsity.


> 2. Is the native Petsc direct solver (using KSPPREONLY and PCLU) designed
> to solve dense system or sparse system?
>

Sparse. We use LAPACK for dense.


> 3. Is the native Petsc direct solver comparable to SuperLU and MUMPS in
> performance? Do they use different algorithms?
>

It is likely slower than SuperLU and not as robust as MUMPS, but there is
no substitute for just running and comparing.

  Thanks,

    Matt


> Thanks in advance for your help.
>
> Best Regards,
> Qin
>


-- 
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/ <http://www.cse.buffalo.edu/~knepley/>
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