Jenetics：我如何在每一步访问进化结果（或统计数据）？

Question

我正在开发基于 Jenetics 框架 (link to jenetics.io) 的优化引擎。我有一个进化引擎定义如下：

final Thread engineStream = new Thread(() -> {
final MinMax<EvolutionResult<DoubleGene, Double>> best = MinMax.of();

_scannerEngine.stream()
    .limit(byPopulationConvergence(convergenceCriterion))
    .limit(result -> !Thread.currentThread().isInterrupted())                              
    .limit(maxGenerations)
    .peek(best).forEach(evolutionResult -> {
        waiting();
        if (callback != null) {
            callback.accept(evolutionResult, best.getMax());
        }
        final String generationCounter = String.valueOf(evolutionResult.getGeneration());
       _callingInstance.doOnAlgorithmCallback(new String("****** finished generation: " + generationCounter + " ****"));
    });
}

engineStream.start();

目前，我正在一个进化周期（通过人口的一次迭代）结束时通过

向我的 UI 推送一条消息

peek(best).forEach(
    ...
    _callingInstance.doOnAlgorithmCallback(...)
)

我想做的是推动进化的当前状态（理想情况下是一些包含当前适应度平均值、最小值、最大值等的统计数据）在执行每个适应度步骤之后，所以用户可以看到优化过程的当前状态。

有什么想法吗？

---

基于 Franz Wilhelmstötter 的建议的最终实施：

final Thread engineStream = new Thread(() -> {
    final MinMax<EvolutionResult<DoubleGene, Double>> best = MinMax.of();

    try {
        _scannerEngine.stream() //
        // stop stream if fitness average across the population is smaller than % of best fitness
        .limit(byFitnessConvergence(5, 20, convergence%)) //
        .limit(interrupted -> !Thread.currentThread().isInterrupted()) //
        .limit(_geneticScanParameters.getMaxGenerationsLimit()) // maximum number of generations
        .peek(best) //
        .peek(_statistics) //
        .forEach(evolutionResult -> {
            waiting();
            if (callback != null) {
                MessageLogger.logError(getClass(), best.getMax().toString());
                if (_geneticScanParameters.getOptimizationStrategy() == Optimize.MAXIMUM) {
                    callback.accept(evolutionResult, best.getMax());
                } else if (_geneticScanParameters.getOptimizationStrategy() == Optimize.MINIMUM) {
                    callback.accept(evolutionResult, best.getMin());
                }
            }
            MessageLogger.log(getClass(), _statistics.toString());
            final String generationCounter = String.valueOf(evolutionResult.getGeneration());
            _callingInstance.doOnAlgorithmCallback(new String("****** finished generation: " + generationCounter + " ****"));
        });

        MessageLogger.log(getClass(), "\n" + _statistics.toString());
    } catch (final Exception ex) {
    MessageLogger.logError(getClass(), Thread.currentThread(), ex);
    }
    _callingInstance.doOnAlgorithmFinished();
});
engineStream.start();
_engineStream = engineStream;

请注意，我使用“_variable”是类属性的约定。

Answer 1

您可以为此目的使用EvolutionStatistics 类。

final Engine<DoubleGene, Double> engine = ...
final EvolutionStatistics<Double, DoubleMomentStatistics> statistics =
    EvolutionStatistics.ofNumber();

final Phenotype<DoubleGene, Double> result = engine.stream()
    .limit(bySteadyFitness(7))
    .limit(100)
    .peek(statistics)
    .collect(toBestPhenotype());

System.println(statistics);

如果您在peek 方法中更新类，您将获得一些额外的统计信息。