On Tue, Apr 21, 2009 at 4:09 PM, Hicham Mouline
<hicham@mouline.org> wrote:
Following my prev message, I wrote the following test on a win platform,
compiled with VS2005 /O2 in release mode
#include <iostream>
#include <boost/variant/variant.hpp>
#include <windows.h>
typedef boost::variant<int, double, char> VT;
struct print_type : public boost::static_visitor<const char*> {
const char* operator()( int )
{
return "int";
}
const char* operator()( double )
{
return "double";
}
const char* operator()( char )
{
return "char";
}
};
int main()
{
const VT v('c');
LARGE_INTEGER usec0, usec1;
const char* volatile res;
QueryPerformanceCounter( &usec0 );
for(size_t s=0; s<2000000; ++s)
res = v.apply_visitor( print_type() );
QueryPerformanceCounter( &usec1 );
std::cout<< (usec1.QuadPart - usec0.QuadPart) <<std::endl;
QueryPerformanceCounter( &usec0 );
for(size_t s=0; s<2000000; ++s)
res = "char";
QueryPerformanceCounter( &usec1 );
std::cout<< (usec1.QuadPart - usec0.QuadPart) <<std::endl;
}
There is no statistically significant difference between the 2 cases.
Can I deduce that at least on this platform, for this code, the visitation
is done at compile-time?