[petsc-users] Questions about AMG and Jacobian Contruction

[Mark Adams]

PETSc has three AMG solvers: GAMG (native) and third party libraries hypre
and ML. This probably what you want.

On Sun, Jul 14, 2019 at 6:25 AM Yingjie Wu via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Respected PETSc developers:
> Hi,
> I have some questions about some functions of AMG and the construction
> time of Jacobian matrix in the process of using. Please help me to answer
> them.
>
> 1. I see some functions about AMG in the list of PETSc functions. I wonder
> if DMDA is necessary to construct vectors when using AMG precondition.
> (Because the geometry described in my PDE is irregular,it contains a lot
> of pipes and connections, instead of using DMDA to manage vectors, I
> define discrete solution vectors by myself.)
>
> 2. As far as I know, besides V-cycle, AMG method also needs auxiliary
> matrix B and transfer matrix P (transfer matrix from fine mesh to coarse
> mesh). Are these transformation matrices built-in or can they be provided
> by users in PETSc?
>
> 3. At present, in my program, I use -snes_mf_operator to solve the
> non-linear PDE problem. Although I do not directly construct Jacobian
> matrix, it is also expensive to construct preconditioning matrix (provided
> by users). Can I control the update and decomposition time of the
> preconditioning matrix, such as updating the preconditioning matrix every
> two Newton steps and then ILU factorization? Can these controls be
> implemented in SNESMonitor?
>
> Thanks,
> Yingjie
>
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