In the beginning I started replying with the standard answer of how java requires jvm startup time which shouldn't be counted and how empty for-loop is not a good measurement, etc. By the time I finished typing the response, there are plenty of other posters responding already. So I did not even bother to send my email.
But it makes me wonder about the jvm startup time, since I heard that it has improved a lot with JSE 5 and 6 (aka 1.5 and 1.6). So I set out to do the experiment with the given parameters of doing a billion iteration of empty loop.
I decided to give the java, C, and C++ a try. My testing environment is Ubuntu 6.10 running in vmware (see my previous post). Details of the environment I used for testing are:
- JSE JDK 5 from Sun
- JSE JDK 6 from Sun
- gcc & g++ 4.1 that came with the Ubuntu
I tested the following source code.
Java:
public class Loop1 {
public static void main(String[] args) {
for (int i = 0; i < 1000000000; i++) ;
}
}
public class Loop2 {
public static void main(String[] args) {
long start = System.currentTimeMillis();
for (int i = 0; i < 1000000000; i++) ;
long end = System.currentTimeMillis();
System.out.println("Time: " + (end - start)/1000.0 + "s");
}
}
C:
int main() {
int i;
for (i = 0; i < 1000000000; i++) ;
return 0;
}
C++:
I used the following commands to compiled those codes:
int main() {
for (int i = 0; i < 1000000000; i++) ;
return 0;
}
- javac Loop1.java
- javac Loop2.java
- gcc loop.c -o loopc
- gcc -O3 loop.c -o loopcO3
- g++ loop.cpp -o loopcpp
- g++ -O3 loop.cpp -o loopcppO3
and I run them with time command 3 times and take the average of the real time output from the time command, in the case of Loop2 I took the average from the output result.
And the result are:
Loop1 (Java5) - 1.793s
Loop2 (Java5) - 1.538s
Loop1 (Java6) - 1.468s
Loop2 (Java6) - 1.233s
loopc - 2.357s
loopcO3 - 0.008s
loopcpp - 2.384s
loopcppO3 - 0.011s
Draw your own conclusion ;P
P.S.: I also tried an empty java program, to see the startup time and to compare it with the removed for-loop for gcc/g++ compiler with -O3 flag. The average result was 0.139 seconds.
