Why is this Dart code so slow compared to java's implementation? - dart

Question

The dart codes as follows is extremely slow compared to java's implementation.
//test.dart
import 'dart:io';
void main(){
for(int i = 0; i < 1 << 25;i++){
stdout.write(i); // or directly print(i);
}
stdout.close();
}
java version:
//Test.java
import java.io.*;
public class Test{
public static void main(String[]args)throws Exception {
try{
PrintWriter out = new PrintWriter(System.out);
for(int i = 0;i < 1 << 25; i++){
out.print(i);
}
out.close();
}catch(Exception e){}
}
}
$ time java Test > /dev/null
real 0m6.421s
user 0m0.046s
sys 0m0.031s
$ time dart Test.dart > /dev/null
real 0m51.978s
user 0m0.015s
sys 0m0.078s
Is stdout/print() unbuffered by default in Dart? Is there something like java's PrintWriter? thanks. (Update: after warming up vm, stdout is 2x slower than java )
real 0m15.497s
user 0m0.046s
sys 0m0.047s
===============================================================================
Update Sep 30, 2013
I have implemented custom buffers for both dart and java codes to make a further comparing,now the result is as follows:
//test.dart
final int SIZE = 8192;
final int NUM = 1 << 25;
void main(){
List<int> content = new List(SIZE);
content.fillRange(0, SIZE, 0);
for(int i = 0; i < NUM;i++){
if(i % SIZE == 0 && i > 0)
print(content);
content[i % SIZE] = i;
}
if (NUM % SIZE ==0)
print(content);
else
print(content.sublist(0, NUM % SIZE));
}
java version:
//Test.java
import java.util.Arrays;
public class Test{
public static final int SIZE = 8192;
public static final int NUM = 1 << 25;
public static void main(String[]args)throws Exception {
try{
int[] buf = new int[SIZE];
for(int i = 0;i < NUM; i++){
if(i % SIZE == 0 && i > 0)
System.out.print(Arrays.toString(buf));
buf[i % SIZE] = i;
}
if(NUM % SIZE == 0)
System.out.print(Arrays.toString(buf));
else
{
int[] newbuf = new int[NUM % SIZE];
newbuf = Arrays.copyOfRange(buf, 0, (NUM % SIZE));
System.out.print(Arrays.toString(newbuf));
}
}catch(Exception e){}
}
}
$ time java Test > /dev/null
real 0m7.397s
user 0m0.031s
sys 0m0.031s
$ time dart test.dart > /dev/null
real 0m22.406s
user 0m0.015s
sys 0m0.062s
As you see, dart is still 3x slower than java.

Answer 1

Maybe your code does not get optimized by the VM.
Only "frequenly" used functions are compiled and executed as native code.
Usually for such benchmark, you have to put the tested code into a function and perform a warmup. For exemple:
//test.dart
import 'dart:io';
void f(nb_shift) {
for(int i = 0; i < 1 << nb_shift;i++){
stdout.write(i); // or directly print(i);
}
}
void main(){
//warm up:
f(3);
// the test
f(25);
stdout.close();
}
Nicolas