The heap scheduler (Scheduler/Heap../ns-2/scheduler.cc)
implements the scheduler using a heap structure.
This structure is superior to the list structure for a large number
of events, as insertion and deletion times are in
for n events.
This implementation in v2 is borrowed from the
MaRS-2.0 simulator [#!Alae94:Design!#];
it is believed that MaRS itself borrowed the code
from NetSim [#!Heyb89:Netsim!#],
although this lineage has not been completely verified.