Port assignment for interconnect reduction in high-level synthesis

This paper focuses on the Port Assignment Problem for Binary Commutative Operators (PAP-BCO) in high-level synthesis. Given a binding of operations and variables, the PAP-BCO pursues to build the connections of registers to functional units with an objective of minimizing the number of interconnections. In this paper, we formulate the PAP-BCO as a vertex partitioning problem on a graph, and propose an exact Integer Linear Programming (ILP) based method and a fast iterative method based on elementary transformations of spanning tree to solve it. Experimental results show that the fast iterative algorithm can get the optimum solutions in 97% runs. At the same time, the running time is only tens of milliseconds for the maximum test case with 64 registers and 140 operations, on which the ILP based method ran out of time.