Strange error on FreeFem++

General Discussion
1

There is a strange behavior on FreeFem++, I’m running my code and for a mesh with h = 0.176777, that means

int globalH = 2^coarseMesh;
mesh calP = square(globalH,globalH);

with coarseMesh = 3
it gives

  -- Square mesh : nb vertices  =81 ,  nb triangles = 128 ,  nb boundary edges 32
  --  mesh:  Nb of Triangles =      1, Nb of Vertices 3
Segmentation fault (core dumped)

but for any other value of coarseMesh it runs without problems, I tried with 0, 1, 2, 4, 5 and 6 and it’s ok, but specifically for 3 it giver segmentarion fault.

Anyone has any idea what might be?

2

Can you post a complete example? I may not like whatever is the 1 triangle
mesh.
Running just what you posted worked but only made one mesh.

3

Just a small remark,

line
– Square mesh : nb vertices =81 , nb triangles = 128 , nb boundary edges 32
come from
mesh calP = square(globalH,globalH);
but the line
– mesh: Nb of Triangles = 1, Nb of Vertices 3
come from with script line ???

the only output is in function :

const Fem2D::Mesh bamg2msh( bamg::Triangles tTh,bool renumbering)

so we need a part of you code if you want idea .

4

it’s from a local mesh

for(int K = 0; K < NbTriangles; K++){

 real coordX0, coordX1, coordX2;
 real coordY0, coordY1, coordY2;

 for(int i = 0; i< NbVertices; i++){
   if(elemNodesGlobal(K,0) == i){
    coordX0 = calP(i).x;
    coordY0 = calP(i).y;
   }
   if(elemNodesGlobal(K,1) == i){
    coordX1 = calP(i).x;
    coordY1 = calP(i).y;
   }
   if(elemNodesGlobal(K,2) == i){
    coordX2 = calP(i).x;
    coordY2 = calP(i).y;
   }
 }


 real[int, int] nodes = [[coordX0, coordY0], [coordX1,coordY1],
                          [coordX2, coordY2]];
 
 //cout << nodes << "\n";

 border f0(t=0,1){P.x=nodes(2,0)*t + nodes(1,0)*(1-t);P.y=nodes(2,1)*t + nodes(1,1)*(1-t); label=11;};
 border f1(t=0,1){P.x=nodes(0,0)*t + nodes(2,0)*(1-t);P.y=nodes(0,1)*t + nodes(2,1)*(1-t); label=22;};
 border f2(t=0,1){P.x=nodes(1,0)*t + nodes(0,0)*(1-t);P.y=nodes(1,1)*t + nodes(0,1)*(1-t); label=33;};
 
 Th[K] = buildmesh(f0(1) + f1(1) + f2(1));
 Th[K] = trunc(Th[K], abs(u0 -K) < 1e-5, split=2^subMesh);

 int NbTrianglesLocal = Th[K].nt;
}
5

What is u0?
I guess if you could attach the complete file that may help.
Certainly the trunc would be suspicious.

6

Hi,

Why do you extract all the vertices to rebuild after the triangle K, instead of extract directly the the triangle K from the global mesh using the function trunc ?

You can do something like this:

mesh calP = square(globalH,globalH);
fespace Tri(calP, P0);
Tri ChiK; 
for(int k = 0; k < NbTriangles; k++){
    ChiK[][k]=1;    // P0 function used to mark the element i
    Th[k]=trunc(calP, ChiK>0.1, split=2^subMesh);      // a mesh made of only one triangle with  refinement 
    ChiK[][k]=0; 
}

Best regards,

Loïc,