[petsc-users] Solving with SNES

behzad baghapour behzad.baghapour at gmail.com
Sat Nov 12 12:10:34 CST 2011

Yes.The Roe average is a common method in this area.
I couldn't understand well what you said about stashing the quantities.
Each residual evaluation is proceeded by a Jacobian one if I choose an
Inexact Newton method and freeze Jacobian matrix for some Newton
iterations. Please make it for me more clear.
Thanks a lot,

On Sat, Nov 12, 2011 at 9:29 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Sat, Nov 12, 2011 at 11:50, behzad baghapour <
> behzad.baghapour at gmail.com> wrote:
>> The nonlinear residual and Jacobian matrix are evaluated with a
>> face-based method. Two integrals are involved (the effect of element
>> internal connections and face flux connections). All of my calculations of
>> flow states are solved and stored in arrays of objects called elements.
> Are you talking about intermediate quantities like Roe averages on face
> quadrature points? The state X at which the residual is evaluated is
> different each time, so you would be using old values if you stashed them.
> The residual might be evaluated multiple times before a Jacobian is
> requested. Normally the residual is much less expensive than the Jacobian,
> so it's not worth stashing the intermediate quantities. See also this FAQ:
> http://www.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#functionjacobian
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