The Doctor Rostering Problem - Asser Fahrenholz

Chapter 4. Solving the DRP 21
Figure 4.4: The rotation principle
this neighborhood and it would then populate the shifts itself. This would then
be similar to the random initial solution.
Figure 4.5: The inversion principle
For each of them, it applies that a random set of shifts are selected, upon which the
function is carried out.
One immediate advantage of these neighborhoods, is that they are simple and easy to
implement. The implementation of these can be found in appendix A.1.
Nielsen [17] also implements the inversion and rotation, which is similar to the insert,
delete and replace moves in the neighborhoods chosen in Meisels and Schaerf [16]. Both
rotation and inversion can be translated to a combination of replace moves. Other than
these sources, very few authors in the literature describe their neighborhood functions
in-depth. This may be due to how the structure and nature of problems often limits the
choices in neighborhoods to a degree, where the choice seems obvious.
It is important to recognise that the generation of neighbors is a factor in the running
time of the entire search. As such, I have placed an upper limit on how many shifts are
randomly selected and used in the neighborhood.