Trad vs. Clang

main.cpp

#include <cstdio>
#include <algorithm>
#include <random>

int main(){
  std::mt19937 mt;
  double s = 0.0;
  std::uniform_real_distribution<double> ud(0.0, 1.0);
  for (int i = 0; i < 1000000; i++) s+=ud(mt);
  printf("%f\n",s);
}

Compile.

FCCpx -Kfast main.cpp -o trad.out
FCCpx -Kfast -Nclang main.cpp -o clang.out

Run (in the interactive queue).

$ time ./trad.out
500044.868973

real    0m0.102s
user    0m0.061s
sys     0m0.029s

$ time ./clang.out
500044.868973

real    0m2.965s
user    0m2.928s
sys     0m0.030s

In the interactive queue.

$ g++ -O3 -std=c++11 main.cpp -o gcc.out
$ time ./a.out
$ time ./gcc.out
500044.868973

real    0m0.256s
user    0m0.255s
sys     0m0.000s