Back to basics: Homogeneous representations of multi-rate synchronous dataflow graphs

Exact temporal analyses of multi-rate synchronous dataflow (MRSDF) graphs, such as computing the maximum achievable throughput, or sufficient buffer sizes required to reach a minimum throughput, require a homogeneous representation called a homogeneous synchronous dataflow (HSDF) graph. The size of such an HSDF graph may, in the worst case, be exponential in the size of the MRSDF graph. In this paper, we revisit the transformation from MRSDF to HSDF, and show how this transformation may be done either exactly or approximately. The approximate transformation gives both an optimistic and a pessimistic HSDF graph, each of which has the same size as the MRSDF graph. We furthermore show how strict lower and upper bounds on throughput, or on the buffer sizes required to reach a minimum throughput, may be obtained from these approximating graphs.