The file `getfem/getfem_assembling.h` defines the functions to compute
and norms of a solution. The following functions compute
the different norms:

```
getfem::asm_L2_norm(mim, mf, U, region = mesh_region::all_convexes());
getfem::asm_H1_semi_norm(mim, mf, U, region = mesh_region::all_convexes());
getfem::asm_H1_norm(mim, mf, U, region = mesh_region::all_convexes());
```

where `mim` is a `getfem::mesh_im` used for the integration, `mf` is a `getfem::mesh_fem` and
describes the finite element method on which the solution is defined, `U` is the
vector of values of the solution on each degree of freedom of `mf` and `region` is an optional parameter which specify the mesh region on which the norm is computed. The size of
`U` should be `mf.nb_dof()`.

In order to compare two solutions, it is often simpler and faster to use the following function than to interpolate one mesh_fem on another:

```
getfem::asm_L2_dist(mim, mf1, U1, mf2, U2, region = mesh_region::all_convexes());
getfem::asm_H1_dist(mim, mf1, U1, mf2, U2, region = mesh_region::all_convexes());
```

These functions return the and norms of .