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Re: [Getfem-users] Problems to build a matrix for a boundary term

 From: Ronan Perrussel Subject: Re: [Getfem-users] Problems to build a matrix for a boundary term Date: Sat, 05 Sep 2009 14:21:04 +0200 User-agent: Thunderbird 2.0.0.23 (X11/20090817)

```Dear Iago,

the exact integration is mainly linked to the use of an affine mesh.
```
Is it the case here? You speak about a circular hole and maybe you use second order transformation for the elements around the hole...
```
I hope it helps.

Best regards,
Ronan

Iago Barbeiro a écrit :
```
```Dear Getfem++ users,

```
I am facing problems to build an elementary matrix using the generic assembly procedure and I hope anyone could give me a hand.
```
```
It is a boundary integral in a two dimensional mesh (It is a circular domain with a circular hole inside and I want to integrate over both boundaries):
```

```
So it is a bilinear form in "p" and "dp" where both are scalars defined with the same fem (mf_p).
```
For that I have tried the following block:

*template<typename MAT> *
*void asm_P_Lap_boundary(const MAT &K_,*
* **                   const mesh_im &mim,*
* **                   const mesh_fem &mf_p, *
* **                   const mesh_region &rg) {*
*
*
*     MAT &K = const_cast<MAT &>(K_);*
*
*
*     getfem::generic_assembly assem;*
*   *
*          *
*     assem.push_mi(mim);*
*     assem.push_mf(mf_p);*
*     assem.push_mat(K);*
*     assem.assembly(rg);*
* }*

Where the mesh_region was built using:

*getfem::mesh_region boundary;*
*getfem::outer_faces_of_mesh(mymesh, boundary);*

But then I found an error message, which is:

*============================================*
*|      An error has been detected !!!      |*
*============================================*
*Error in getfem_mat_elem.cc, line 121 : *
*Exact integration not allowed in this context*

```
Why exact integration would not be allowed here? Am I doing something wrong? Any light?
```

Iago C. Barbeiro
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```