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"