Intel Compiler vs. GCC

main.cpp

#include <random>
int main() {
  std::mt19937 mt;
  std::uniform_real_distribution<> ud(0.0, 1.0);
  for (int j = 0; j <10000; j++) {
    for (int i = 0; i < 10000; i++) {
      if (i%2) ud(mt);
    }
  }
}

Environment

• CPU: Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz
• OS: SUSE Linux Enterprise Server 11 (x86_64)
• g++ (GCC) 5.4.0
• icpc (ICC) 18.0.5 20180823

$ g++ -O3 -march=native -Wall -Wextra -std=c++11  main.cpp -o gcc.out
$ icpc -O3 -xHOST -Wall -Wextra -std=c++11  main.cpp -o icpc.out
$ time ./gcc.out
./gcc.out  0.25s user 0.00s system 96% cpu 0.265 total

$ time ./icpc.out
./icpc.out  4.56s user 0.00s system 99% cpu 4.572 total