Question

我已经通过k-means为终止条件定义了一个过滤器。如果我运行我的应用程序，它总是只计算一次迭代。

我认为问题在于：

var positionWatchId;

function addWatch(){
    positionWatchId = navigator.geolocation.watchPosition(onWatchPositionSuccess, onWatchPositionError, options);
}

function clearWatch(){
    navigator.geolocation.clearWatch(positionWatchId);
}


function onWatchPositionError(err) {
    window.plugins.toast.showLongBottom('App is waiting for location service! ', function (a) {
    }, function (b) {
    })
    if (watchpositionErrorCount >= 9) {        
        clearWatch();
        addWatch();
    }
    watchpositionErrorCount++;
}

addWatch();

或者过滤器功能：

DataSet<GeoTimeDataCenter> finalCentroids = loop.closeWith(newCentroids, newCentroids.join(loop).where("*").equalTo("*").filter(new MyFilter()));

最好的问候，保罗

我的完整代码：

public static final class MyFilter implements FilterFunction<Tuple2<GeoTimeDataCenter, GeoTimeDataCenter>> {

    private static final long serialVersionUID = 5868635346889117617L;

    public boolean filter(Tuple2<GeoTimeDataCenter, GeoTimeDataCenter> tuple) throws Exception {
        if(tuple.f0.equals(tuple.f1)) {
            return true;
        }
        else {
            return false;
        }
    }
}

Answer 1

我认为问题是过滤功能（以你未发布的代码为模）。 Flink的终止标准以下列方式工作：如果提供的终止DataSet为空，则满足终止标准。否则，如果未超过最大迭代次数，则启动下一次迭代。

Flink的filter函数仅保留FilterFunction返回true的元素。因此，使用MyFilter实现，您只能保持迭代前后的质心相同。这意味着如果所有质心都已更改，您将获得空DataSet，因此迭代终止。这显然与实际终止标准相反。终止标准应该是：只要存在已经改变的质心，就用k-means继续。

您可以使用coGroup函数执行此操作，如果前一个质心DataSet没有匹配的质心，则会发出元素。这类似于左外连接，只是您放弃非空匹配。

public static void main(String[] args) throws Exception {
    // set up the execution environment
    final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

    DataSet<Element> oldDS = env.fromElements(new Element(1, "test"), new Element(2, "test"), new Element(3, "foobar"));
    DataSet<Element> newDS = env.fromElements(new Element(1, "test"), new Element(3, "foobar"), new Element(4, "test"));

    DataSet<Element> filtered = newDS.coGroup(oldDS).where("*").equalTo("*").with(new FilterCoGroup());

    filtered.print();
}

public static class FilterCoGroup implements CoGroupFunction<Element, Element, Element> {

    @Override
    public void coGroup(
            Iterable<Element> newElements,
            Iterable<Element> oldElements,
            Collector<Element> collector) throws Exception {

        List<Element> persistedElements = new ArrayList<Element>();

        for(Element element: oldElements) {
            persistedElements.add(element);
        }

        for(Element newElement: newElements) {
            boolean contained = false;

            for(Element oldElement: persistedElements) {
                if(newElement.equals(oldElement)){
                    contained = true;
                }
            }

            if(!contained) {
                collector.collect(newElement);
            }
        }
    }
}

public static class Element implements Key {
    private int id;
    private String name;

    public Element(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public Element() {
        this(-1, "");
    }

    @Override
    public int hashCode() {
        return 31 + 7 * name.hashCode() + 11 * id;
    }

    @Override
    public boolean equals(Object obj) {
        if(obj instanceof Element) {
            Element element = (Element) obj;

            return id == element.id && name.equals(element.name);
        } else {
            return false;
        }
    }

    @Override
    public int compareTo(Object o) {
        if(o instanceof Element) {
            Element element = (Element) o;


            if(id == element.id) {
                return name.compareTo(element.name);
            } else {
                return id - element.id;
            }
        } else {
            throw new RuntimeException("Comparing incompatible types.");
        }
    }

    @Override
    public void write(DataOutputView dataOutputView) throws IOException {
        dataOutputView.writeInt(id);
        dataOutputView.writeUTF(name);
    }

    @Override
    public void read(DataInputView dataInputView) throws IOException {
        id = dataInputView.readInt();
        name = dataInputView.readUTF();
    }

    @Override
    public String toString() {
        return "(" + id + "; " + name + ")";
    }
}

apache flink - 过滤作为终止条件

1 个答案: