VLSI design: gate matrix layout problem 18. VLSI design: gate matrix layout problem

With applications ranging from fields as distinct as fuzzy modeling (Xiong 2001), autonomous robot behavior (Luk et al. 2001), learning with backpropagation (Foo et al. 1999), and multicriteria optimization (Viennet et al. 1996), evolutionary methods have become an indispensable tool for systems scientists. Although already studied in the past, an interesting emerging issue is the use of multiple populations, which is gaining increased momentum from the conjunction of two technologies. On the hardware side, computer networks, multi-processor computers and distributed processing systems (such as workstations clusters) are increasingly becoming widespread. Regarding the software issues, the introduction of Parallel Virtual Machine (PVM), and later the Message Passing Interface Standard (MPI), as well as web-enabled, object-oriented languages (such as Java) have also had their role. Most Evolutionary Algorithms (EAs) are methods that are easy to parallelize as well as naturally suitable for heterogeneous systems. For most EAs the distribution of the tasks is relatively easy for most applications. The workload can be distributed at an individual or a population level; the final choice depending on the complexity of the computations involved. The application presented in this chapter is motivated by the availability of these computer environments. However, here we do not report results on the use of parallel computers, or networks of workstations. The proposed memetic algorithm (MA) runs in a sequential way on a single processor, but a set of populations evolve separately, an approach that can be easily mapped to a parallel environment. Species evolve naturally grouped in sub-populations, with boundaries defined by some specific features like distance or geographical barriers. The role of closed (or nearly closed) populations in biological evolution is extremely important. Consider for instance the Galapagos Islands, an example of notorious inspirational role for Darwin’s ideas when aboard the HMS Beagle (Darwin 1993). A set of islands separated by several kilometers of water can be colonized by a single species of birds. In the beginning of such colonization, all animals will share the same characteristics (and genetic pool), but as evolution takes place, the groups concentrated in each island will start to differentiate by adapting themselves to the particular characteristics present in each island (Weiner 1995). This independent adaptation