Eric Niebler schrieb:
Did you turn on compiler optimizations? If not, the results are meaningless. If you did, please post the full source code. What you posted was incomplete.
sorry..yes I have turned on compiler optimization. #include <algorithm> #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics.hpp> #include <boost/algorithm/minmax_element.hpp> #include <boost/array.hpp> #include <boost\chrono\chrono.hpp> using namespace boost; using namespace boost::chrono; using namespace std; typedef array<int,10000000> dataarray; dataarray data; int _tmain(int argc, _TCHAR* argv[]) { high_resolution_clock::time_point start = high_resolution_clock::now(); high_resolution_clock::time_point stop = high_resolution_clock::now(); for(unsigned int i = 0; i< data.size();i++) { data[i] = i; } start = high_resolution_clock::now(); dataarray::iterator resmin = std::min_element(data.begin(),data.end()); dataarray::iterator resmax = std::max_element(data.begin(),data.end()); stop = high_resolution_clock::now(); cout<<"min_element,max_element:"<<duration_cast<milliseconds>(stop-start).count()<<endl; cout<<"minVal="<<*resmin<<",maxVal="<<*resmax<<endl; boost::accumulators::accumulator_set<int, boost::accumulators::features<boost::accumulators::tag::min,boost::accumulators::tag::max>> acc; start = high_resolution_clock::now(); acc = std::for_each(data.begin(),data.end(),acc); stop = high_resolution_clock::now(); int minVal = boost::accumulators::extract_result< boost::accumulators::tag::min >(acc); int maxVal = boost::accumulators::extract_result< boost::accumulators::tag::max >(acc); cout<<"min_max: accumulator:"<<duration_cast<milliseconds>(stop-start).count()<<endl; cout<<"minVal="<<minVal<<",maxVal="<<maxVal<<endl; start = high_resolution_clock::now(); pair< vector<int>::iterator, vector<int>::iterator > result = boost::minmax_element(data.begin(), data.end()); stop = high_resolution_clock::now(); cout<<"min_max: minmax_element:"<<duration_cast<milliseconds>(stop-start).count()<<endl; cout<<"minVal="<<*result.first<<",maxVal="<<*result.second<<endl; minVal = (std::numeric_limits<int>::max)(); maxVal = (std::numeric_limits<int>::min)(); start = high_resolution_clock::now(); for(dataarray::iterator it = data.begin(); it!=data.end();it++) { minVal = (std::min)(minVal,*it); maxVal = (std::max)(maxVal,*it); } stop = high_resolution_clock::now(); cout<<"min/max handcoded:"<<duration_cast<milliseconds>(stop-start).count()<<endl; cout<<"minVal="<<minVal<<",maxVal="<<maxVal<<endl; return 0; }