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added Robin BC, disabled cuthill_mckee_reordering for now

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jakob.schratter 2026-01-24 20:58:53 +01:00
commit b78c3f9aff
5 changed files with 46 additions and 46 deletions
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13
mgrid_2/geom.cpp
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@ -759,6 +759,11 @@ const std::vector<int> Mesh::BoundaryEdges() const
return _ebedges;
}
const std::vector<int> Mesh::BoundaryEdgeNodes() const
{
return _bedges;
}
// Only the outer edges for Robin BC
void Mesh::InitializeOuterEdges()
@ -996,12 +1001,16 @@ Mesh::Mesh(std::string const &fname)
//Debug();
DeriveEdgeFromVertexBased(); // Generate also the edge based information
{
// Cuthill-McKee reordering
// Increases mesh generation time by factor 5 - but solver is faster.
auto const perm = cuthill_mckee_reordering(_edges);
PermuteVertices_EdgeBased(perm);
// auto const perm = cuthill_mckee_reordering(_edges);
// PermuteVertices_EdgeBased(perm);
}
DeriveVertexFromEdgeBased();

1
mgrid_2/geom.h
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@ -331,6 +331,7 @@ private:
public:
const std::vector<int> BoundaryEdges() const;
const std::vector<int> BoundaryEdgeNodes() const;
std::vector<int> OuterEdgesSubdomains;
std::vector<int> OuterEdges;

75
mgrid_2/getmatrix.cpp
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@ -616,57 +616,48 @@ void FEM_Matrix::ApplyDirichletBC(std::vector<double> const &u, std::vector<doub
}
void FEM_Matrix::ApplyRobinBC_mult(std::vector<double> const &u, std::vector<double> &f, const double u_out)
void FEM_Matrix::ApplyRobinBC_mult(std::vector<double> &f, const double u_out)
{
auto const RobinEdges = _mesh.OuterEdges;
auto const RobinEdgesSubdomains = _mesh.OuterEdgesSubdomains;
for (int i = 0; i < RobinEdges.size(); ++i)
auto const BoundaryEdges = _mesh.BoundaryEdges();
auto const BoundaryEdgeNodes = _mesh.BoundaryEdgeNodes();
assert (BoundaryEdgeNodes.size() == 2* BoundaryEdges.size());
vector<double> Coordinates = _mesh.GetCoords();
for (size_t i = 0; i < RobinEdges.size(); ++i)
{
cout << "Edge number " << RobinEdges[i] << ", subdomain: " << RobinEdgesSubdomains[i] << endl;
//cout << "Edge number " << RobinEdges[i] << ", subdomain: " << RobinEdgesSubdomains[i] << " " << endl;
double alpha = Heat_transfer_coefficient(RobinEdgesSubdomains[i]);
}
int const EdgeNode1 = BoundaryEdgeNodes[2*i];
int const EdgeNode2 = BoundaryEdgeNodes[2*i + 1];
double x_1 = Coordinates[EdgeNode1];
double y_1 = Coordinates[EdgeNode1 + 1];
double x_2 = Coordinates[EdgeNode2];
double y_2 = Coordinates[EdgeNode2 + 1];
double EdgeLength = sqrt((x_2 - x_1)*(x_2 - x_1) + (y_2 - y_1)*(y_2 - y_1));
int ii = _id[EdgeNode1];
int jj = _id[EdgeNode2];
int ij = fetch(_ik[_id[EdgeNode1]], EdgeNode1);
int ji = fetch(_ik[_id[EdgeNode2]], EdgeNode2);
_sk[ii] += EdgeLength*alpha/3;
_sk[jj] += EdgeLength*alpha/3;
_sk[ij] += EdgeLength*alpha/6;
_sk[ji] += EdgeLength*alpha/6;
f[ii] += EdgeLength*alpha*u_out/2;
f[jj] += EdgeLength*alpha*u_out/2;
// Jakob Todo
auto const idx = _mesh.Index_DirichletNodes(); // ALL boundary nodes
const vector<int> sd_vec = _mesh.ElementSubdomains;
for (int i = 0; i < idx.size(); ++i) {
int const row = idx[i];
int subdomain = sd_vec[row];
// cout << "row: " << row;
// cout << ", subdomain: " << subdomain << endl;
double alpha = Heat_transfer_coefficient(subdomain);
f[row] += u_out*alpha/2;
for (int ij = _id[row]; ij < _id[row + 1]; ++ij)
{
int const col = _ik[ij];
if(col == row)
{
_sk[ij] += alpha/3;
}
else
{
int const id1 = fetch(col, row); // Find entry (col,row)
assert(id1 >= 0);
_sk[id1] += alpha/6;
}
}
}
return;
@ -681,7 +672,7 @@ double FEM_Matrix::Heat_transfer_coefficient(const int subdomain)
{
// outside
case 0:
alpha = 1.0;
alpha = 10.0;
break;
// ceramic
@ -691,12 +682,12 @@ double FEM_Matrix::Heat_transfer_coefficient(const int subdomain)
// water
case 2:
alpha = 1.0;
alpha = 500.0;
break;
// air
case 3:
alpha = 1.0;
alpha = 10.0;
break;
default:

3
mgrid_2/getmatrix.h
View file

@ -410,11 +410,10 @@ class FEM_Matrix: public CRS_Matrix
* The <a href="https://www.jstor.org/stable/2005611?seq=1#metadata_info_tab_contents">penalty method</a>
* is used for incorporating the given values @p u.
*
* @param[in] u (global) vector with Dirichlet data
* @param[in] u_out outside temperature
* @param[in,out] f load vector
*/
void ApplyRobinBC_mult(std::vector<double> const &u, std::vector<double> &f, const double u_out);
void ApplyRobinBC_mult(std::vector<double> &f, const double u_out);
double Heat_transfer_coefficient(const int subdomain);

8
mgrid_2/main.cpp
View file

@ -33,7 +33,7 @@ int main(int argc, char **argv )
//gMesh_Hierarchy ggm(mesh_c, nrefine);
//const Mesh &mesh = ggm.finest();
//mesh.Debug();
//mesh.DebugEdgeBased();
//mesh_c.DebugEdgeBased();
// Initializing FEM matrix !pattern! (only zero entries now)
@ -55,7 +55,7 @@ int main(int argc, char **argv )
// Calculate RHS
SK.CalculateRHS(fv, [](double x, double y) {return 0;});
//SK.CheckRowSum();
SK.CheckMatrix();
//SK.CheckMatrix();
// Initialize temperature
@ -65,7 +65,7 @@ int main(int argc, char **argv )
mesh_c.Init_Solution_mult(uv, 2, [](double x, double y) -> double { return 18; }); // air
// Apply BC
SK.ApplyRobinBC_mult(uv, fv, 18.0);
SK.ApplyRobinBC_mult(fv, 18.0);
// Solve
@ -74,7 +74,7 @@ int main(int argc, char **argv )
auto t3 = system_clock::now(); // start timer
// JacobiSolve(SK, fv, uv ); // solve the system of equations
//JacobiSolve(SK, fv, uv ); // solve the system of equations
auto t4 = system_clock::now(); // stop timer
auto duration = duration_cast<microseconds>(t4 - t3); // duration in microseconds