[petsc-users] Parallel computing in SNES

[Matthew Knepley]

On Tue, Dec 10, 2024 at 4:32 AM David Jiawei LUO LIANG <
12431140 at mail.sustech.edu.cn> wrote:

> Hello PETSc,
>
> I want to substitute the existing nonlinear solver codes with SNES.
>
> The existing code is Parallel computing.
>
> My FormFunction and FormJacobian is attached in file Res_Jac.cpp.
>
> The global tangent matrix assembly and residual function assembly are both
> implemented by invoking user pointers.
>
> The following is the message, we can find that SNES just iterate once.
>
>
> I think the problem is input solution Vec y doesn't link to Residual Vec
> f, because my update is stored in the user variables.
> If I use
> const PetscScalar *yy;
> VecGetArrayRead(y, &yy);
> the value of yy is not identical to Vec y, because there are multi thread.
>
> So, my problem is how to assembly residual and tangent in parallel
> environment?
>

I am having trouble understanding your question.

1) Can you run with -snes_monitor -snes_converged_reason
-ksp_monitor_true_residual -ksp_converged_reason -snes_view and send the
output?

2) You have the line

VecCopy(user->gassem_ptr->G, f);

which looks like it puts the values of your G into f, so I am not sure what
the problem is.

  THanks,

     Matt


>
> David Jiawei LUO LIANG
>
> 南方科技大学/学生/研究生/2024
>
> 广东省深圳市南山区学苑大道1088号
>
>


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