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

Ryan Yan vyan2000 at gmail.com
Tue Jan 26 10:13:18 CST 2010

Hi Matt,
Thanks a lot for the suggestion.


On Tue, Jan 26, 2010 at 5:46 AM, Matthew Knepley <knepley at gmail.com> wrote:

> You might try the pseudo-transient continuation code.
>   Matt
> 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 lead.
> -- Norbert Wiener
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