Performance testing in C++
While developing a message-driven system we’ve come to a problem of what type of object creation/destruction uses less system resources: stack or heap. And although you maybe know the answer it’s always interesting to measure to be sure. We’ve done it with the help of unit-testing.
First a test object have been created:
class TestObject
{
public:
explicit TestObject(vector a, vector b) : mv1(a), mv2(b)
{
}
vector mv1;
vector mv2;
};
Another version of test object is using const reference for parameters:
class TestObject
{
public:
explicit TestObject(const vector &a, const vector&b) : mv1(a), mv2(b)
{
}
vector mv1;
vector mv2;
};
Now we test memory allocation for 1 million test objects and measure time:
void testAllocHeap()
{
vector a(0,0,0);
vector b(1,1,1);
time_type startTime = local_time();
for(int i=0; i<1000000; i++)
{
TestObject *pointerToTestObject = new TestObject(a, b);
delete pointerToTestObject;
}
time_type stopTime = local_time();
std::cout << "Time heap: " << stopTime-startTime <<"n";
}
void testAllocStack()
{
vector a(0,0,0);
vector b(1,1,1);
time_type startTime = local_time();
for(int i=0; i<1000000; i++)
{
TestObject pointerToTestObject(a, b);
}
time_type stopTime = local_time();
std::cout << "Time stack: " << stopTime-startTime << "n";
}
Our measurements show that object creation as a const reference on stack is approximately 20 times more efficient then object allocation on heap.
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