Management of a collection of processes, some subsets of which share memory, utilizes both the monitor and message-passing parts of the p4 library. In addition, there are routines for identifying a ``cluster master'' process in each cluster (p4_am_i_cluster_master), finding out the number of clusters (p4_num_cluster_ids), and finding out the process identifiers of the processes in one's own cluster (p4_get_cluster_ids). These routines and others support the explicit expression of algorithms that take advantage of the cluster environment.