The hamming shell recombination strategy is illustrated in figure 9. The local search directs the offspring to the nearest locally optimal point which is operated on in the next generation by the traditional genetic recombination operators. Large Step Optimisation, as GLS, is an example of a bilevel local search technique. We will consider the following problem. There is a finite set of jobs and a set of parallel, identical machines.
All jobs are available at the current time.
Each job requires processing on any one of the machines. Each job s processing time is uncertain. The TA algorithm is much better than the IM method although, the results of both are very poor even though they are run for the same time as the GLS and SA approaches. This is partly due to the fact that on some of the harder instances the SA and GLS techniques are run for between 2 and 15 hours. The subproblems are solved by a constraint propagation approach which finds good solutions by fixing arc directions.