Chapter 5: Writing a Benchmark

Data Functions

Data functions are useful for creating benchmarks that compare multiple data inputs, for example locale aware compare against standard compare.

 void TestBenchmark::multiple_data()
 {
     QTest::addColumn<bool>("useLocaleCompare");
     QTest::newRow("locale aware compare") << true;
     QTest::newRow("standard compare") << false;
 }

The test function then uses the data to determine what to benchmark.

 void TestBenchmark::multiple()
 {
     QFETCH(bool, useLocaleCompare);
     QString str1 = QLatin1String("This is a test string");
     QString str2 = QLatin1String("This is a test string");

     int result;
     if (useLocaleCompare) {
         QBENCHMARK {
             result = str1.localeAwareCompare(str2);
         }
     } else {
         QBENCHMARK {
             result = (str1 == str2);
         }
     }
 }

The "if(useLocaleCompare)" switch is placed outside the QBENCHMARK macro to avoid measuring its overhead. Each benchmark test function can have one active QBENCHMARK macro.