AmorphousSpaceSpatialWorker has a sparse matrix representation from the world. It is very effective in finding the elements by their indices, however, it may be very slow in some of the cases, e.g., when iterating all of the elements.
Since AmorphousSpaceSpatialWorker#step() iterates all of the cells one-by-one, it may cause a serious performance issue (however, it is used only for the GUI template).
Iterating should be done as suggested in the documentation of the used API:
http://acs.lbl.gov/software/colt/api/cern/colt/matrix/impl/SparseObjectMatrix2D.html