Issue details

The implementation in https://github.com/mumax/3/blame/master/cuda/exchangedecode.cu "averages" the exchange by taking the sum of the exchange with a cell's 4 (or 6 in 3D) neighbours, but never divides by this number of neigbours.
The result therefore is factor 4 or 6 too large.

Thanks @ElizabethMJefremovas for spotting this