RoundTest.cpp

alex@alex-xubuntu:/tmp$ clang++ -std=c++11 -lopencv_core -o test \
>   -Ofast -march=native -mtune=native -ffast-math RoundTest.cpp
alex@alex-xubuntu:/tmp$ ./test
1: sum = 0, time = 3.75455
2: sum = 6250000, time = 0.428553
3: sum = -6250000, time = 0.429368
4: sum = 99999993, time = 0.371513
5: sum = 0, time = 0.447814
6: sum = 0, time = 0.370834
7: sum = 0, time = 0.371188
8: sum = 0, time = 0.86279
alex@alex-xubuntu:/tmp$ g++ -std=c++11 -o test -Ofast -march=native -mtune=native -ffast-math RoundTest.cpp -lopencv_core
alex@alex-xubuntu:/tmp$ ./test
1: sum = 0, time = 1.28906
2: sum = 6250000, time = 1.25554
3: sum = -6250000, time = 1.25936
4: sum = 99999993, time = 0.43766
5: sum = 0, time = 1.04787
6: sum = 0, time = 0.317587
7: sum = 0, time = 0.339587
8: sum = 0, time = 0.315362