qt-creator/tests/auto/mapreduce/tst_mapreduce.cpp

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#include <utils/algorithm.h>
#include <utils/mapreduce.h>

#include <QtTest>

class tst_MapReduce : public QObject
{
    Q_OBJECT

private slots:
    void mapReduce();
};

static int returnxx(int x)
{
    return x*x;
}

static void returnxxThroughFutureInterface(QFutureInterface<int> &fi, int x)
{
    fi.reportResult(x*x);
}

void tst_MapReduce::mapReduce()
{
    const auto dummyInit = [](QFutureInterface<double>& fi) -> double {
        fi.reportResult(0.);
        return 0.;
    };
    const auto reduceWithFutureInterface = [](QFutureInterface<double>& fi, double &state, int value) {
        state += value;
        fi.reportResult(value);
    };
    const auto reduceWithReturn = [](double &state, int value) -> double {
        state += value;
        return value;
    };
    const auto cleanupHalfState = [](QFutureInterface<double> &fi, double &state) {
        state /= 2.;
        fi.reportResult(state);
    };

    // TODO: cannot use function returnxx without pointer here because of decayCopy of arguments in runAsync
    {
        QList<double> results = Utils::mapReduce(QList<int>({1, 2, 3, 4, 5}),
                                                 dummyInit, &returnxx,
                                                 reduceWithFutureInterface, cleanupHalfState)
                .results();
        Utils::sort(results); // mapping order is undefined
        QCOMPARE(results, QList<double>({0., 1., 4., 9., 16., 25., 27.5}));
    }
    {
        QList<double> results = Utils::mapReduce(QList<int>({1, 2, 3, 4, 5}),
                                                 dummyInit, &returnxxThroughFutureInterface,
                                                 reduceWithFutureInterface, cleanupHalfState)
                .results();
        Utils::sort(results); // mapping order is undefined
        QCOMPARE(results, QList<double>({0., 1., 4., 9., 16., 25., 27.5}));
    }
    {
        QList<double> results = Utils::mapReduce(QList<int>({1, 2, 3, 4, 5}),
                                                 dummyInit, &returnxx,
                                                 reduceWithReturn, cleanupHalfState)
                .results();
        Utils::sort(results); // mapping order is undefined
        QCOMPARE(results, QList<double>({0., 1., 4., 9., 16., 25., 27.5}));
    }
}

QTEST_MAIN(tst_MapReduce)

#include "tst_mapreduce.moc"