[petsc-dev] How to get L and D from cholesky factorisation ?

[Hong]

mumps stores  LDLt using its private internal data structure, which is not
exposed to user and can be used only via mumps API.
Either ask mumps developer about it or use a debugger to step into mumps
source code.

Hong

On Thu, Aug 24, 2017 at 9:46 AM, Franck Houssen <franck.houssen at inria.fr>
wrote:

> How to get L (as a Mat) and D (probably as a Vec) from cholesky
> factorisation ?
>
> I googled and looked in the doc but didn't find any obvious answer. I am
> not sure to get the steps to follow: is there a dedicated example ?
>
> To make it short, I have:
> PCSetType(pc, PCCHOLESKY); // LDLt
> PCFactorSetMatSolverPackage(pc, "mumps");
> PCFactorGetMatrix(pc, &f);
> MatGetInertia(f, ....); // OK !
>
> Now, I would like to get/see L and D: how to get them ?
>
> From petsc/src/ksp/ksp/examples/tutorials/ex52.c, I would say
> MatGetDiagonal(f, D) returns D: correct ? If so, how to get L as well ?
>
> A related question would be : how to get L and U from a PCLU factorisation
> ?
>
> Franck
>
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