Dear all,

For viewing the DG solution in Paraview, we firstly run the following codes to get the solution “gfu”.

```
from netgen.geom2d import unit_square
from ngsolve import *
mesh = Mesh(unit_square.GenerateMesh(maxh=0.3))
order=4
fes = L2(mesh, order=order, dgjumps=True)
u,v = fes.TnT()
jump_u = u-u.Other()
jump_v = v-v.Other()
n = specialcf.normal(2)
mean_dudn = 0.5*n * (grad(u)+grad(u.Other()))
mean_dvdn = 0.5*n * (grad(v)+grad(v.Other()))
alpha = 4
h = specialcf.mesh_size
a = BilinearForm(fes)
diffusion = grad(u)*grad(v) * dx \
+alpha*order**2/h*jump_u*jump_v * dx(skeleton=True) \
+(-mean_dudn*jump_v-mean_dvdn*jump_u) * dx(skeleton=True) \
+alpha*order**2/h*u*v * ds(skeleton=True) \
+(-n*grad(u)*v-n*grad(v)*u)* ds(skeleton=True)
a += diffusion
a.Assemble()
f = LinearForm(fes)
f += 1*v*dx
f.Assemble()
gfu = GridFunction(fes, name="uDG")
gfu.vec.data = a.mat.Inverse() * f.vec
```

Then we run the following code to get a vtk file “solution”,

```
vtk = VTKOutput(ma=mesh, coefs=[gfu], names=["uh"], filename="solution", subdivision=3)
vtk.Do()
```

But when we view this vtk file on Paraview, it is a totally bad file and we cannot see anything. Please tell us where something is wrong.

Best,

Di Yang