Qt Reference Documentation

containers.cpp Example File

qtestlib/tutorial5/containers.cpp
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 // This file contains benchmarks for comparing QVector against std::vector

 #include <QtCore>
 #include <QVector>
 #include <vector>

 #include <qtest.h>

 template <typename T> // T is the item type
 class UseCases {
 public:
     virtual ~UseCases() {}

     // Use case: Insert \a size items into the vector.
     virtual void insert(int size) = 0;

     // Use case: Lookup \a size items from the vector.
     virtual void lookup(int size) = 0;
 };

 template <typename T>
 T * f(T *ts) // dummy function to prevent code from being optimized away by the compiler
 {
     return ts;
 }

 // This subclass implements the use cases using QVector as efficiently as possible.
 template <typename T>
 class UseCases_QVector : public UseCases<T>
 {
     void insert(int size)
     {
         QVector<T> v;
         T t;
         QBENCHMARK {
             for (int i = 0; i < size; ++i)
                 v.append(t);
         }
     }

     void lookup(int size)
     {
         QVector<T> v;

         T t;
         for (int i = 0; i < size; ++i)
             v.append(t);

         T *ts = new T[size];
         QBENCHMARK {
             for (int i = 0; i < size; ++i)
                 ts[i] = v.value(i);
         }
         f<T>(ts);
         delete[] ts;
     }
 };

 // This subclass implements the use cases using std::vector as efficiently as possible.
 template <typename T>
 class UseCases_stdvector : public UseCases<T>
 {
     void insert(int size)
     {
         std::vector<T> v;
         T t;
         QBENCHMARK {
             for (int i = 0; i < size; ++i)
                 v.push_back(t);
         }
     }

     void lookup(int size)
     {
         std::vector<T> v;

         T t;
         for (int i = 0; i < size; ++i)
             v.push_back(t);

         T *ts = new T[size];
         QBENCHMARK {
             for (int i = 0; i < size; ++i)
                 ts[i] = v[i];
         }
         f<T>(ts);
         delete[] ts;
     }
 };

 struct Large { // A "large" item type
     int x[1000];
 };

 // Symbian devices typically have limited memory
 #ifdef Q_OS_SYMBIAN
 #  define LARGE_MAX_SIZE 2000
 #else
 #  define LARGE_MAX_SIZE 20000
 #endif

 class tst_vector_vs_std : public QObject
 {
     Q_OBJECT
 public:
     tst_vector_vs_std()
     {
         useCases_QVector_int = new UseCases_QVector<int>;
         useCases_stdvector_int = new UseCases_stdvector<int>;

         useCases_QVector_Large = new UseCases_QVector<Large>;
         useCases_stdvector_Large = new UseCases_stdvector<Large>;
     }

 private:
     UseCases<int> *useCases_QVector_int;
     UseCases<int> *useCases_stdvector_int;
     UseCases<Large> *useCases_QVector_Large;
     UseCases<Large> *useCases_stdvector_Large;

 private slots:
     void insert_int_data();
     void insert_int();
     void insert_Large_data();
     void insert_Large();
     void lookup_int_data();
     void lookup_int();
     void lookup_Large_data();
     void lookup_Large();
 };

 void tst_vector_vs_std::insert_int_data()
 {
     QTest::addColumn<bool>("useStd");
     QTest::addColumn<int>("size");

     for (int size = 10; size < 20000; size += 100) {
         const QByteArray sizeString = QByteArray::number(size);
         QTest::newRow(("std::vector-int--" + sizeString).constData()) << true << size;
         QTest::newRow(("QVector-int--" + sizeString).constData()) << false << size;
     }
 }

 void tst_vector_vs_std::insert_int()
 {
     QFETCH(bool, useStd);
     QFETCH(int, size);

     if (useStd)
         useCases_stdvector_int->insert(size);
     else
         useCases_QVector_int->insert(size);
 }

 void tst_vector_vs_std::insert_Large_data()
 {
     QTest::addColumn<bool>("useStd");
     QTest::addColumn<int>("size");

     for (int size = 10; size < LARGE_MAX_SIZE; size += 100) {
         const QByteArray sizeString = QByteArray::number(size);
         QTest::newRow(("std::vector-Large--" + sizeString).constData()) << true << size;
         QTest::newRow(("QVector-Large--" + sizeString).constData()) << false << size;
     }
 }

 void tst_vector_vs_std::insert_Large()
 {
     QFETCH(bool, useStd);
     QFETCH(int, size);

     if (useStd)
         useCases_stdvector_Large->insert(size);
     else
         useCases_QVector_Large->insert(size);
 }

 void tst_vector_vs_std::lookup_int_data()
 {
     QTest::addColumn<bool>("useStd");
     QTest::addColumn<int>("size");

     for (int size = 10; size < 20000; size += 100) {
         const QByteArray sizeString = QByteArray::number(size);
         QTest::newRow(("std::vector-int--" + sizeString).constData()) << true << size;
         QTest::newRow(("QVector-int--" + sizeString).constData()) << false << size;
     }
 }

 void tst_vector_vs_std::lookup_int()
 {
     QFETCH(bool, useStd);
     QFETCH(int, size);

     if (useStd)
         useCases_stdvector_int->lookup(size); // Create a std::vector and run the benchmark.
     else
         useCases_QVector_int->lookup(size); // Create a QVector and run the benchmark.
 }

 void tst_vector_vs_std::lookup_Large_data()
 {
     QTest::addColumn<bool>("useStd");
     QTest::addColumn<int>("size");

     for (int size = 10; size < LARGE_MAX_SIZE; size += 100) {
         const QByteArray sizeString = QByteArray::number(size);
         QTest::newRow(("std::vector-Large--" + sizeString).constData()) << true << size;
         QTest::newRow(("QVector-Large--" + sizeString).constData()) << false << size;
     }
 }

 void tst_vector_vs_std::lookup_Large()
 {
     QFETCH(bool, useStd);
     QFETCH(int, size);

     if (useStd)
         useCases_stdvector_Large->lookup(size);
     else
         useCases_QVector_Large->lookup(size);
 }

 QTEST_MAIN(tst_vector_vs_std)
 #include "main.moc"
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