Sorts and removes all duplicate entries of a dvector. Note that the internal
buffer size remains unchanged. To reduce the buffer size, call
dvector_shrink_to_fit.
Nodes of different colours represent the following:
Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module. Where possible, edges connecting nodes are given different colours to make them easier to distinguish in large graphs.