translate python grad(u).trans code to C++

Kai
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3 years 1 month ago #4017 by Kai

translate python grad(u).trans code to C++ was created by Kai

Hi all

,
i try to translate the following piece of python code

Code:

self.u = self.fes.TrialFunction()
self.v = self.fes.TestFunction()
# StiffnessMatrix depending on material type:
if (self.material.type == "linear"):
   self.A = BilinearForm(self.fes)
   self.A += 2 * self.material.mu * InnerProduct(1 / 2 * (grad(self.u) + grad(self.u).trans),
                                                        1 / 2 * (grad(self.v) + grad(self.v).trans)) * dx

into corresponding C++ code so far i have

Code:

ngcomp::ProxyNode u = fes->GetTrialFunction();
ngcomp::ProxyNode v = fes->GetTestFunction();

Flags flags_bfa;
std::shared_ptr<T_BilinearFormSymmetric<double>> bfa = make_shared<T_BilinearFormSymmetric<double>> (fes, "a", flags_bfa);

bfa->AddIntegrator(make_shared<SymbolicBilinearFormIntegrator>(
                   material.mu * InnerProduct(
                    0.5f*(u->Deriv() + TransposeCF(u->Deriv())),
                    0.5f*(v->Deriv() + TransposeCF(v->Deriv()))),
                   VOL, VOL));

but the TransposeCF leads to

Code:

terminate called after throwing an instance of 'ngcore::Exception'
  what():  Transpose of non-matrix called
00:46:50: Das Programm ist abgestürzt.

So my question is how can i transpose v->Deriv() and u->Deriv() ?

Thank you for any help

joachim
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3 years 1 month ago #4019 by joachim

Replied by joachim on topic translate python grad(u).trans code to C++

Hi Kai,

can you show us how you created the finite element space fes ? Is it really vector-valued ?

For debugging, you can insert a

Code:

cout << *(u->Deriv()) << endl;

before the exception is thrown.

Joachim

Kai
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3 years 1 month ago #4020 by Kai

Replied by Kai on topic translate python grad(u).trans code to C++

Hi Joachim,
thanks for quick response, i used the wrong FESpace. Now iam using VectorH1FESpace but the next problem follows : the SymbolicBilinearFormIntegrator does not work with Vector valued Coefficient functions ...

hope this is ok to attach my new qustion here in this thread ?

joachim
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3 years 1 month ago #4021 by joachim

Replied by joachim on topic translate python grad(u).trans code to C++

yes, at the end you need a scalar-valued function for the SymbolicBilinearFormIntegrator.

You get it, for example, by taking InnerProduct(grad(u), grad(v)).
grad(u) and grad(v) are matrix-valued.

Kai
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Junior Member

3 years 1 month ago #4022 by Kai

Replied by Kai on topic translate python grad(u).trans code to C++

But i do already the InnerProduct like InnerProdukt(grad(u) + Transpose(grad(u)), grad(v) + Transpose(grad(v)))

Code:

bfa->AddIntegrator(make_shared<SymbolicBilinearFormIntegrator>(
                   material.mu * InnerProduct(
                    0.5f*(u->Deriv() + TransposeCF(u->Deriv())),
                    0.5f*(v->Deriv() + TransposeCF(v->Deriv()))),
                   VOL, VOL));

but this returns a coef innerproduct, fix size = 9, real ... i do not see whats wrong here ... mathematically this should work ?

joachim
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3 years 1 month ago #4023 by joachim

Replied by joachim on topic translate python grad(u).trans code to C++

can you do a

Code:

auto func = material.mu * InnerProduct(
                    0.5f*(u->Deriv() + TransposeCF(u->Deriv())),
                    0.5f*(v->Deriv() + TransposeCF(v->Deriv())));
cout << *func << endl;

and send the output ?

If this does not help, you may send the complete example.

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