Efficient Exploration Of Search Space Research Articles

Cell assignment in hybrid CMOS/nanodevices architecture using Tabu Search

A recent advancement in VLSI that drastically improved the circuit density is the introduction of CMOL (CMOS/nanodevices hybrid), which consists of an overlay of a nanofabric over a CMOS stack. Combinational logic in CMOL is implemented from a netlist of NOR gates and Inverters by programming nanodevices placed between overlapping nanowires. The length of the nanowires is restricted, and therefore connectivity of the circuit elements is constrained to be within a certain radius, else additional buffers are required. In this paper we present a Tabu Search (TS) algorithm to address the assignment problem in CMOL. The heuristic is engineered to provide sub-optimal solution by efficient exploration of search space. Empirical results for ISCAS benchmarks are compared with previous solutions using GA, MA, and LRMA heuristics. Results show that in almost all cases, TS exhibits more intelligent search of the solutions subspace, and is able to find better solutions in less time. For all tested benchmarks, over 90 % reduction in average CPU processing time when compared with best published techniques was obtained.