Rheolef  7.1
an efficient C++ finite element environment
neumann-laplace-lambda.cc
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1 #include "rheolef.h"
26 using namespace rheolef;
27 using namespace std;
28 size_t d;
29 Float f (const point& x) { return 1; }
30 Float g (const point& x) { return -0.5/d; }
31 int main(int argc, char**argv) {
32  environment rheolef (argc, argv);
33  geo omega (argv[1]);
34  d = omega.dimension();
35  space Xh (omega, argv[2]);
36  trial u (Xh); test v (Xh);
37  form a = integrate (dot(grad(u),grad(v)));
38  field b = integrate(v);
39  field lh = integrate (f*v) + integrate ("boundary", g*v);
40  form A = {{ a, b},
41  { trans(b), 0}};
42  field B = { lh, 0};
43  A.set_symmetry(true);
44  space IR = space::real();
45  space Yh = Xh*IR;
46  field Uh (Yh,0);
47  problem p (A);
48  p.solve (B, Uh);
49  dout << catchmark("u") << Uh[0];
50  // get lambda:
51  Float lambda = (Uh.comm().rank() == Uh.constraint_process_rank()) ? Uh[1].dof(0) : 0;
52 #ifdef _RHEOLEF_HAVE_MPI
53  mpi::broadcast (Uh.comm(), lambda, Uh.constraint_process_rank());
54 #endif // _RHEOLEF_HAVE_MPI
55  dout << catchmark("lambda") << lambda << endl;
56  check_macro(fabs(lambda) < 1e-10, "unexpected lambda="<<lambda);
57 }
field lh(Float epsilon, Float t, const test &v)
see the Float page for the full documentation
see the field page for the full documentation
see the form page for the full documentation
see the geo page for the full documentation
see the point page for the full documentation
see the problem page for the full documentation
see the catchmark page for the full documentation
Definition: catchmark.h:67
see the environment page for the full documentation
Definition: environment.h:115
odiststream dout(cout)
see the diststream page for the full documentation
Definition: diststream.h:430
see the space page for the full documentation
see the test page for the full documentation
see the test page for the full documentation
This file is part of Rheolef.
csr< T, sequential > trans(const csr< T, sequential > &a)
trans(a): see the form page for the full documentation
Definition: csr.h:455
rheolef::std enable_if ::type dot const Expr1 expr1, const Expr2 expr2 dot(const Expr1 &expr1, const Expr2 &expr2)
dot(x,y): see the expression page for the full documentation
Definition: vec_expr_v2.h:415
std::enable_if< details::is_field_convertible< Expr >::value,details::field_expr_v2_nonlinear_terminal_field< typename Expr::scalar_type,typename Expr::memory_type,details::differentiate_option::gradient >>::type grad(const Expr &expr)
grad(uh): see the expression page for the full documentation
std::enable_if< details::is_field_expr_v2_nonlinear_arg< Expr >::value &&! is_undeterminated< Result >::value, Result >::type integrate(const geo_basic< T, M > &omega, const Expr &expr, const integrate_option &iopt, Result dummy=Result())
see the integrate page for the full documentation
Definition: integrate.h:202
size_t d
int main(int argc, char **argv)
Float f(const point &x)
Float g(const point &x)
rheolef - reference manual
Definition: cavity_dg.h:29
Definition: cavity_dg.h:25
Definition: sphere.icc:25
Definition: leveque.h:25
Float u(const point &x)