Anders Logg wrote:
On Fri, Mar 13, 2009 at 07:48:39PM +0100, Patrick Riesen wrote:
Patrick Riesen wrote:
Anders Logg wrote:
On Wed, Mar 11, 2009 at 10:21:52AM +0100, Patrick Riesen wrote:
hello
So my Etafunction is now being correctly constructed and there are
the
correct values in the dof-vector(). i did this by a function class
definition and a call to Eta as
class Eta: public Function
{
Eta (Mesh& mesh, Function& gamma, Form& form, ...) :
Function(mesh,
form, argument_id)
{ constructor....something as above }
and then i call it as
f_eta = new Eta(.....);
in the main program.
calling Eta as Function(mesh,form,id) i thought this should create a
discrete function for f_eta, but the type of the f_eta function is
'user'. this gives me an error at the assembly, "missing eval() for
user-defined function..."
do i have to add an dummy eval() function to my Eta-class, or what
do i
have to change that no eva()-missing error is raised and my f_eta
function is of type discrete?
thanks for your help,
patrick
sorry, i found an error, now the Eta is of type discrete (all 3
argument
functions of my form are now discrete). but the eval() error at
assembly
of the form is still present.
Have you called vector() inside the constructor of Eta? That should
make it discrete and the assembler should not complain. Perhaps there
is some other function in you form that is missing an eval (or a
vector).
hi anders,
yes i did that, and now i found the error fortunately. i did not
initialize the bilinear form correctly with some placeholder function
for Eta. now the assembly is working, so i can go on.
thank you & regards,
patrick
hi all
my code is now running but the Eta-funcs still give me some problems. i
have initialized my bilinear/linear form with two constant functions as
f_eta = new Function(mesh, 1.)
f_Deta = new Function(mesh, 1.)
Are you using an old version? This doesn't work with the current
interface.
the first newton iteration gives me a newtonian solution from which i
take the velocity to compute the invariant in another form (gamma) and
then i construct the discussed functions Eta, DEta, and renew f_eta,
f_Deta as
f_eta = new Eta(gamma,.....)
f_Deta = new DEta(gamma,......)
so i guess in the second iteration it will assemble with a variable
viscosity as f_eta, f_Deta are different now but it just converges to
the newtonian solution.
is this a problem, that i constructed the forms with a constant
function? does dolfin then not consider the values in the vector() of
the new discrete functions for f_eta, f_Deta after renewing?
Yes, if you construct your form with some Function, then that Function
will be used. The form won't change just because you create a new
Function later.
hi,
thanks again for the help so far,
now i think i managed to construct my forms correctly and the code is
running. the solution looks reasonable, starting from newtonian solution
with n=1 and then changes when the powerlaw exponent is increased.
however, the convergence is poor, e.g. with a powerlaw exponent of n=2
it takes almost 30 iterations to converge (incremental criterium) and it
does not converge beyond n=2 so far.
to compute the variable viscosity terms in my form i followed the
example of the quadrature elements implementation of the nonlinear
poisson demo (sect. 6.10 in the ffc manual from nov 2008) and solve a
linear system with another form-file to obtain the invariant of the
strain tensor. then as discussed in previous mails (see above) i take
power n-something of the invariant and compute the viscosity in the
dof-vector adaptively in each iteration.
is there a way to play around with the newtonsolver? now i use a
lu-factorization with umfpack and ublas-backend, i just
had
NewtonSolver newtonsolver;
e.g but i tried the same as
NewtonSolver newtonsolver(lu,default_pc);
i got an error:
In file included from PowerlawStokesSolver.cpp:4:
PowerlawStokesSolver.h:74: error: 'lu' is not a type
PowerlawStokesSolver.h:74: error: 'default_pc' is not a type
BTW: i use dolfin0.8.1 with dolfin-grade2
regards,
patrick
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