I have a function that gets a QStringList
as a parameter.
The QStringList
is created in place for parameter passing. Two possibilities come to my mind for this:
myFunction(QStringList() << myQString); // possibility 1
myFunction(QStringList { myQString }); // possibility 2
Which possibility is more performant?
Here is the benchmark:
#define ct_Benchmark(EXPR, repeat){\
int repeated = repeat;\
qint64 initialTime = QDateTime::currentMSecsSinceEpoch();\
qint64 totalTime = initialTime;\
EXPR;\
initialTime = QDateTime::currentMSecsSinceEpoch() - initialTime;\
for ( int ___i_ = 0; ___i_ < repeated; ___i_++) {\
EXPR;\
}\
totalTime = QDateTime::currentMSecsSinceEpoch() - totalTime;\
qreal averageTime = qreal( totalTime / repeated );\
const QString expression(#EXPR);\
const QString iterations(" Cycles: " + QString::number( repeated ) );\
const QString initial ("Initial: " + QString::number( initialTime ) );\
const QString total (" Total: " + QString::number( totalTime ) );\
const QString average ("Average: " + QString::number( averageTime, 'g', 24 ) );\
ct_Info(expression, iterations, initial, total, average);\
}
QString sneed("'s feed & seed. Formerly chucks.");
ct_Benchmark( QStringList{ sneed }, 1000000 );
ct_Benchmark( QStringList( QStringList() << sneed ), 1000000 );
Info /home/anon/Programming/QtConsoleDesigner/QtSandbox/src/sandbox.cpp:57
int main(int, char**)
QString expression
"QStringList( QStringList() << sneed )"
QString iterations
" Cycles: 10000000"
QString initial
"Initial: 0"
QString total
" Total: 3461"
QString average
"Average: 0"
Info /home/anon/Programming/QtConsoleDesigner/QtSandbox/src/sandbox.cpp:56
int main(int, char**)
QString expression
"QStringList{ sneed }"
QString iterations
" Cycles: 10000000"
QString initial
"Initial: 0"
QString total
" Total: 2094"
QString average
"Average: 0"
Info /home/anon/Programming/QtConsoleDesigner/QtSandbox/src/sandbox.cpp:57
int main(int, char**)
QString expression
"QStringList( QStringList() << sneed )"
QString iterations
" Cycles: 10000000"
QString initial
"Initial: 0"
QString total
" Total: 545"
QString average
"Average: 0"
Info /home/anon/Programming/QtConsoleDesigner/QtSandbox/src/sandbox.cpp:56
int main(int, char**)
QString expression
"QStringList{ sneed }"
QString iterations
" Cycles: 10000000"
QString initial
"Initial: 0"
QString total
" Total: 379"
QString average
"Average: 0"
Compiled using GCC.
Possibility 1 QStringList{ sneed }
is about a third faster.