Hi, the method `prolongateP1ToP2()` of the `P2Function` class seems to not work correctly. It is supposed to fill the P2Function object with data obtained from embedding the given P1Function into the corresponding P2 FE-space on the same mesh and refinement level. The following figure is the result of embedding a constant P1 function. As one can see there are errors at the macro edges. These seem to be associated with the left- and right-most edgeDoF at the edge:  Note that while the method is tested as part of `P2P1TransferTest`, that test appears to only test inside a single macro face, while using zero values at edges and vertices. This would explain why it does not catch the problem. Cheers Marcus