[petsc-users] Fwd: nonzero prescribed boundary condition

[Jed Brown]

On Thu, Sep 8, 2011 at 14:58, Tian(ICT) <rongtian at ncic.ac.cn> wrote:

> By 50 iterations, I meant my implementation of this prescribed boundary
> condition was not working,
> not converging. Yes, I put 1 on the diagonal.\
>

Is the system singular? What equations are you solving? Do boundary
conditions give you a constant null space? Incompressible flow is this way.

Run with -ksp_monitor_true_residual -pc_type lu -snes_view and send the
output.


> Can I just enforce the solution x within each Newton iteration to the
> prescribed values to satisfy the prescribed boundary condition, not
> MatZeroRowsing Jacobian?
>

It's important for the linear system to be nonsingular.
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