# [deal.II] Re: multiply constrained dofs (hanging nodes+periodic) fails a simple test case

```Hi Sambit,

On Saturday, April 7, 2018 at 6:51:37 PM UTC+2, Sambit Das wrote:
>
> Hello dealii-team,
>
> I have created a failing test case in serial when hanging nodes+periodic
> constraints are mixed.
>
> *The algorithm of the test is follows: (attached *
> *minimalExampleHangingNodesPeriodicConstraintsBug.cc)*
>
> 1) Create a hypercube (-20,20) with origin at the center
>
> 2) Set periodic boundary conditions on the hypercube
>
> 3) Perform two levels of mesh refinement:- a) one step uniform refinement
> hypercube to get 8 cells ,and b) then pick one of the 8 cells and refine
> only that cell which creates hanging nodes on the faces. Finally I get 15
> cells (see attached image).
>
> 4) Create two constraintMatrices: *constraints* and
> *onlyHangingNodeConstraints.*
> *                constraints:* both hanging node and periodic constraints
>                  *onlyHangingNodeConstraints:* just hanging node
> constraints
>
> 5) Create two nodal vectors vec1 and vec2 with nodal value =
> nodal_coordinate.norm(). Set and distribute vec1 using  *constraints. *Set
> and distribute vec2 using *onlyHangingNodeConstraints.*
>
> 6) Print l2 norm of vec1 and vec2.
>
> *The issue:*
>
> Since the nodal value = nodal_coordinate.norm() is intrinsically periodic
> (the domain being a hypercube with origin at the center), I would expect
> vec1 and vec2 to have the same l2 norm. However I get different l2 norm
> values:
>```
```
I don't think that's the case. The domain is indeed periodic, but this is
completely detached from location of support/nodal points.
Same applies to geometry, you will have different coordinates of vertices
across the PBC so

Point<3> nodalCoor = cellDof->vertex(i);

is expected to give different values on the opposite boundaries.

Regards,
Denis.

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