Edge to element

General Discussion
1

Hello everyone,

how do I create an edge to element matrix using FreeFem++?
So, basically, given the edge number, I would like to know the elements that share that edge. Is it possible?

2

yes,

the finite element P0edge build a edge, and

// the corresponding edge in the adjacent triangle
  Th[k] == Th[k].adj(e) ;// non adjacent triangle return the same 
  Th[k] != Th[k].adj(e) ;// true adjacent triangle
3

yeah, i did that

//----------------Numbering edges-------------------
fespace L0(calP, P0edge);
int ndofL0K = L0.ndofK;

real[int, int] edgesinK(NbTriangles, ndofL0K);
for(int i=0; i<NbTriangles; i++){
    for(int j=0; j<ndofL0K; j++){
        edgesinK(i,j) = L0(i,j);
    }
}
cout << edgesinK << "\n";

but then I tried this and it’s not working

for(int i=0; i<L0.ndofK; i++){
    for(int K=0; K<NbTriangles; K++){
        // non adjacent triangle return the same
        if(calP[K]==calP[K].adj(i)){
            cout << K << "\n";
        }
        // true adjacent triangle 
        else if(calP[K] != calP[K].adj(i)){
            cout << K << "\n";
        }
        
    }
}
4

Hello,

The problem is that the value of “i” is modified when you do calP[K].adj(i).

Just copy the value of i in a new variable j.

for(int i=0; i<L0.ndofK; i++){
    for(int K=0; K<NbTriangles; K++){
        // non adjacent triangle return the same
        int j = i; 
        if(calP[K]==calP[K].adj(j)){
            cout << K << "\n";
        }
        // true adjacent triangle 
        else if(calP[K] != calP[K].adj(j)){
            cout <<  calP[K].adj(j) << "\n";
        }
        
    }
}

Best regards,

Loïc

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