On Mon, Oct 25, 2010 at 1:54 PM, Daniel Walker <daniel.j.walker@gmail.com> wrote:
On Sat, Oct 23, 2010 at 3:00 PM, Domagoj Saric <dsaritz@gmail.com> wrote:
"Daniel Walker" <daniel.j.walker@gmail.com> wrote in message news:AANLkTikXL0i5Z+NoO2a3TiB8q2RmTk4oHJ1kzOyR-7vE@mail.gmail.com...
Do you have any suggestion for how to quantify this? I've run some simple benchmarks, but in optimized object code the time overhead of boost::function is so small it's hard to measure.
Those benchmarks are obviously lacking...I've given you examples that show that the various overheads of the current implementation are quite measurable...
Sorry, I must have missed your examples. Here's a simple benchmark that we could use:
template<class T> double benchmark(T f, int n) { assert(f); boost::timer t; for(int i = 0; i < n; ++i) f(i); return t.elapsed(); }
int echo(int x) { return x; }
int main() { int n = INT_MAX; boost::function<int(int)> f = &echo;
double baseline = benchmark(&echo, n); double t = benchmark(f, n); assert(baseline < t);
std::cout << "boost::function overhead = " << (t - baseline) / n << " seconds" << std::endl; return 0; }
On my machine, this measures the overhead of boost::function as 2 nanoseconds, though, obviously, this is a statistical inference and quantities of time that small are hard to measure.
I've found that such benchmarks, while able to produce long mailing list discussions, don't have much practical value. Do you have a performance problem with the current boost::function? An actual program or application which would run noticeably faster with the 2 nanoseconds per call speedup? Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode