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Last active July 24, 2016 15:04
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/* Solve the poisson problem
on a circle with homogeneous boundary conditions
and f = x*y
NOTE : The extension .cpp is used only
for illustration in github gists as
syntax highlighting is not available for FreeFEM++.
The actual extension for FreeFEM++ is .edp.
If you want to run the file, download it as ff++.edp and run it.
bool debug = false;
border Gamma1(t=0,2*pi){x=cos(t); y=sin(t);}; //Define the boundary
border Gamma2(t=0,2*pi){x=0.3*cos(t); y=0.3*sin(t);}
mesh Th = buildmesh(Gamma1(100)+Gamma2(-100)); //Triangulation Th
fespace Vh(Th, P1); //Construct the finite element space Th with P1 elements.
Vh u,v; // Functions u and v are picewise linear functions
func f = x*y; //Define a function f=x*y
real cpu = clock();
solve Prob(u,v,solver=LU) = int2d(Th)(dx(u)*dx(v)+dy(u)*dy(v)) //LHS of the weak form (Bilinear term)
- int2d(Th)(f*v) //RHS - Linear term
+ on(Gamma1,u=0) //Dirichlet boundary condition
+ on(Gamma2,u=0);
ofstream ff("graph.txt");
for (int i=0; i<Th.nt; i++)
for(int j=0; j<3; j++)
ff<<Th[i][j].x<<" "<<Th[i][j].y<<" "<<u[][Vh(i,j)]<<endl;
ff<<Th[i][0].x<<" "<<Th[i][0].y<<" "<<u[][Vh(i,0)]<<"\n\n\n";
cout<<"Cpu Time = "<<clock()-cpu<<endl;
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