Because the parallelisation is at the cluster level there are some situations, whereby instead of
optimisation being faster when running on multiple slaves, the optimisation will be slower. <br>
This is the case when all spins being studied in is clustered into a small number of clusters. <br>
It is also likely to be slower for the minimise user function when no clustering is defined, due to the
overhead costs of data transfer (but for the numeric models, in this case there will be a clear win).