@Override
public LocalSearchResult call() throws Exception {
// get initial solution
TTPSolution initialSolution = constructionHeuristic.getInitialSolution();
LocalSearchStatistics localSearchStatistics = null;
if (collectStatistics) {
localSearchStatistics = new LocalSearchStatistics();
localSearch.setLocalSearchStatistics(localSearchStatistics);
}
// apply local search
TTPSolution lsSolution = localSearch.doLocalSearch(initialSolution);
// logger.info("Iter: " + iteration + " Current Solution: " +
// lsSolution.getCost());
return new LocalSearchResult(iteration, lsSolution, localSearchStatistics);
}
@Override
public TTPSolution doSearch(TTPInstance instance) {
if (searchStatistics != null) searchStatistics.start();
ExecutorService executorService = Executors.newFixedThreadPool(noThreads);
List<LocalSearchCallable> localSearches = new ArrayList<LocalSearchCallable>(noTries);
constructionHeuristic.setProblemInstance(instance);
try {
for (int i = 0; i < noTries; i++) {
IConstructionHeuristics<TTPInstance, TTPSolution> clonedConstructionHeuristic =
constructionHeuristic.clone();
ILocalSearch<TTPSolution> clonedLocalSearch = localSearch.clone();
localSearches.add(
new LocalSearchCallable(
clonedConstructionHeuristic, clonedLocalSearch, i, searchStatistics != null));
}
} catch (CloneNotSupportedException e) {
logger.error("Failed to create clone for multi-threaded local search", e);
}
try {
List<Future<LocalSearchResult>> solutions = executorService.invokeAll(localSearches);
TTPSolution bestSolution = null;
for (Future<LocalSearchResult> futureSolution : solutions) {
try {
LocalSearchResult result = futureSolution.get();
TTPSolution solution = result.getSolution();
if (solution == null) {
logger.warn("Solution was null");
continue;
}
if (searchStatistics != null)
searchStatistics.addLocalSearchStatistic(result.getIteration(), result.getStatistics());
if (solution != null
&& (bestSolution == null || solution.getCost() < bestSolution.getCost()))
bestSolution = solution;
} catch (ExecutionException e) {
logger.warn("One of the local search executors failed", e);
e.printStackTrace();
}
}
executorService.shutdown();
if (searchStatistics != null) {
searchStatistics.end();
searchStatistics.setSolution(bestSolution);
}
return bestSolution;
} catch (InterruptedException e) {
logger.error("Failed to do multi-threaded local search", e);
if (searchStatistics != null) {
searchStatistics.setException(e);
searchStatistics.end();
}
return null;
}
}
