Benchmarks how QList::reserve() affects QList performance

benchqlist.cpp

// Build with: g++ benchqlist.cpp -o benchqlist -I/usr/include/qt4 -Wall -lQtCore -lstdc++ -O2
#include <QtCore/QList>
#include <QtCore/QElapsedTimer>
#include <QtCore/QDebug>

#if 1
#define ELEMENT int
#define ELEMENT_VALUE 12

#else

struct MyStruct {
    int x, y;
    QString text;
    char data[100];
};

#define ELEMENT MyStruct
#define ELEMENT_VALUE MyStruct()
#endif

int main(int argc, char *argv[])
{
    if (argc < 2) {
        qWarning() << "Usage: benchqlist [-r] <number-of-iterations>";
        return 1;
    }
    bool reserve = false;
    QString arg = QString::fromUtf8(argv[1]);
    if (arg == "-r") {
        reserve = true;
        Q_ASSERT(argc == 3);
        arg = QString::fromUtf8(argv[2]);
    }
    bool ok;
    int count = arg.toInt(&ok);
    Q_ASSERT(ok);

    qWarning() << "Testing with" << count << "elements," << (reserve ? "using reserve" : "not using reserve");
    QList<ELEMENT> list;
    if (reserve) {
        list.reserve(count);
    }

    QElapsedTimer timer;
    timer.start();
    for (int x = count - 1; x >= 0; --x) {
        list.append(ELEMENT_VALUE);
    }
    qWarning() << timer.elapsed() / 1000.;
}