Optimizing Synchronization in Multiprocessor Implementations of Iterative Dataflow Programs

The execution time or estimated execution time of actor. UBS Unbounded buffer synchronization. A synchronization protocol that must be used for feedforward edges of the synchronization graph. This protocol requires four synchronization accesses per iteration period. t v () v 68 Glossary Same as with the DFG understood from context. If there is no path in from to , then ; otherwise, , where is any minimum-delay path from to. Given a path , is the sum of the edge delays over all edges in. Represents an edge whose source and sink vertices are and , respectively, and whose delay is equal to. Represents the maximum cycle mean of a DFG. BBS Bounded buffer synchronization. A synchronization protocol that may be used for feedback edges in a synchronization graph. This protocol requires two synchronization accesses per schedule period. critical cycle A fundamental cycle in a DFG whose cycle mean is equal to the maximum cycle mean of the DFG. cycle mean The cycle mean of a cycle in a DFG is equal to , where is the sum of the execution times of all vertices on , and is the sum of delays of all edges in. estimated throughput Given a DFG with execution time estimates for the actors, the estimated throughput is the reciprocal of the maximum cycle mean. feedback edge An edge that is contained in at least one cycle. feedforward edge An edge that is not contained in a cycle. maximum cycle mean Given a DFG, the maximum cycle mean is the largest cycle mean over all fundamental cycles in the DFG. SCC Strongly connected component. self-timed buffer bound Given a feedback edge in a synchronization graph, the self-timed buffer bound is an upper bound on the number of tokens that can simultaneously reside on (the buffer size). synchronization access An access to shared memory that used to update or examine the status of a synchronization variable. synchronization cost The average number of synchronization accesses that must be performed per iteration period in the self timed implementation of a ρ x y , () ρ G G ρ G x y , () G x y ρ G x y , () ∞ = ρ G x y , () p () Delay = p x y p () Delay p p () Delay p d n u v , () u v n λ max C …