[petsc-users] How to find a good initial guess for a BVP

Matthew Knepley knepley at gmail.com
Tue Jan 26 04:46:47 CST 2010

You might try the pseudo-transient continuation code.


On Mon, Jan 25, 2010 at 9:03 PM, Ryan Yan <vyan2000 at gmail.com> wrote:

> Hi All,
> Hopefully, this is not considered as an off-topic thread. Since I got snes
> converged reason -6.
> Can anyone please share some hints on how to find a good inital guess?
> I am solving a nonlinear BVP(steady-states) extracted from a time-dependent
> problem by setting d/dt=0. The equation is conservational law for mass,
> momentum, internal energy, with an algebraic heating source. After all,
> v(velocity), P(pressure), U(fluid internal energy), can be solved from this
> coupled system. I am using Newton's method for this nonlinear system.
> Frankly, I do not have a good initial guess for the solver. The only
> information that I have is the inital condition for the time-dependent
> problem, where the BVP comes from. I have tried my solver with different
> inital guess for many times, but with no luck of a satisfying residual
> reduction.
> So, do I have to solve the time-dependent problem after a long time
> stepping to get a steady solution? Or is there any better way of finding a
> good initial guess?
> Any suggestion is highly appreciated.
> Yan

What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
-- Norbert Wiener
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