C++ vs Java speed(Loops with Arithmetic) -


the following small programs compute sum of numbers 1 1 billion we're written in c++ , java closely write them. understanding c++ "faster" language, java version of code completes in ~.5 seconds vs ~3 seconds c++.

c++ (gcc compiler):

int main(){     long long x = 0;     (long i=0;i<1000000001;i++){     x=x+i;     }     cout << x << endl;     return 0; }

java:

public class main {     public static void main(string[] args)  {         long x=0;         (long i=0;i<1000000001;i++){             x=x+i;         }         system.out.println(x);      }  }

how 1 optimize c++ code fast java version? possible?

if compile optimizations, c++ version considerably faster.

java: 

javac main.java  $ time java main 500000000500000000  real    0m0.727s user    0m0.724s sys     0m0.004s

c++: 

clang -o3 main.cpp -o cpp  $ time ./cpp  500000000500000000  real    0m0.003s user    0m0.000s sys     0m0.000s

my clang version: 

$ clang --version clang version 4.0.0-1ubuntu1 (tags/release_400/rc1) target: x86_64-pc-linux-gnu thread model: posix installeddir: /usr/bin

my java version: 

$ javac -version javac 1.8.0_144

the reason optimization slow process; quicker compilation times if turn optimizations off. better development, defaults clang developers chose. java faster because more optimizations @ run-time. jvm bytecode not that different source-code compiled from!


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