2: OK; rank and tag used

3:
E5: DebugVector(): numprocs iterations (cumbersome)

E6: OK

E7: MinMax: no global exchange [-0.5]

E8: Allroallv: three versions realized [+0.5]

4:
E9: only the initialization from template has been used, not the coordinates [-1]

E10: _sendbuf is vector<double>
VecAccu(...int..) not correct [-1]
check data from rank 1

E11:
Global_Nodes() wrong result [-2]
Interface nodes counted multiple times.

E12: Ok

E13: not available