Circuit Retiming

Years and Authors of Summarized Original Work

• 1991; Leiserson, Saxe

Problem Definition

Circuit retiming is one of the most effective structural optimization techniques for sequential circuits. It moves the registers within a circuit without changing its function. Besides clock period, retiming can be used to minimize the number of registers in the circuit. It is also called minimum area retiming problem Leiserson and Saxe [3] started the research on retiming and proposed algorithms for both minimum period and minimum area retiming. Both their algorithms for minimum area and minimum period will be presented here.

The problems can be formally described as follows. Given a directed graph G = (V, E) representing a circuit – each node v ∈ V represents a gate and each edge e ∈ E represents a signal passing from one gate to another – with gate delays $d : V \rightarrow \mathbb{R}^{+}$ and register numbers $w : E \rightarrow \mathbb{N}$, the minimum area problem asks for a relocation of...