  The problem of finding a spanning forest of a graph in a
distributed-processing environment is studied. If an input graph is weighted,
then the goal is to find a minimum-weight spanning forest. The processors
communicate by broadcasting. The output consists of the edges that make a
spanning forest and have been broadcast on the network. Input edges are
distributed among the processors, with each edge held by one processor.
  The underlying broadcast network is implemented as a multiple-access channel.
If exactly one processor attempts to perform a broadcast, then the broadcast is
successful. A message broadcast successfully is delivered to all the processors
in one step. If more than one processors broadcast simultaneously, then the
messages interfere with each other and no processor can receive any of them.
  Optimality of algorithmic solutions is investigated, by way of comparing
deterministic with randomized algorithms, and adaptive with oblivious ones.
Lower bounds are proved that either justify the optimality of specific
algorithms or show that the optimal performance depends on a class of
algorithms.
