翻译 | QMap与QHash小基准

/* Copyright 2013 Olivier Goffart <ogoffart@woboq.com>
http://woboq.com/blog/qmap_qhash_benchmark.html
*/

#include <QtCore/QtCore>
#include <unordered_map>

#ifndef CONTAINER
#error CONTAINER must be defined to QMap, QHash, std::map or std::unordered_map
#endif

namespace std{
/* std::hash specialization for QString so it can be used
  * as a key in std::unordered_map */
template<class Key> struct hash;
template<> struct hash<QString> {
    typedef QString Key;
    typedef uint result_type;
    inline uint operator()(const QString &s) const { return qHash(s); }
};
}


int main(int argc, char **argv) {
    if (argc < 2)
        qFatal("Missing number of element to add");

    QByteArray a = argv[1];
    uint num = a.toUInt();

    // creates an array of random keys
    QVector<QString> strs(num);
    for (int i=0; i < num; ++i)
        strs[i] = qvariant_cast<QString>(qrand());

    CONTAINER<QString, QString> c;
    for (uint i = 0; i < num; ++i) {
        QString &k = strs[i];
        c[k] = QString::number(i);
    }

    quint64 it = 0;
    const QString *arr = strs.constData();

    QElapsedTimer t;
    t.start();

    while (t.elapsed() < 1000) {
        const QString &k = arr[(++it)*797%num];
        c[k]; // perform a lookup
    }
    qDebug() << it/1000;
}