Dear Getfem users,
i wanted to solve a simple laplacian with pure Neumann boundary condition on a
cube.
In order to do so, since the problem is ill-posed, i added the following
constraint on the unknown u
int_omega u dx=0
via a Lagrangian multiplier.
In the code, the left-hand side is defined by
Model.add_fem_variable("u", mf_u);
getfem::add_linear_generic_assembly_brick(model, mim, "(Grad_u.Grad_Test_u)");
model.add_fixed_size_variable("lambda", 1);
getfem::add_linear_generic_assembly_brick(model, mim, "(lambda*Test_u)");
getfem::add_linear_generic_assembly_brick(model, mim, "(u*Test_lambda)");
If i am not mistaken, it should correspond to the left hand side described in
https://fenicsproject.org/olddocs/dolfin/1.3.0/python/demo/documented/neumann-poisson/python/documentation.html
for instance
As a result, the mean value is relatively small in comparison with u (while not
exactly 0).
However, when i run the program, i get the following warning:
Level 2 Warning in ../../src/gmm/gmm_vector.h, line 592: Inefficient addition
of element in rsvector with **** non-zero entries
Did i do something wrong? If i didn't, is it possible to disable this warning?
Thanks in advance,
David.
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