What did java do here for being so fast ?

[tribal hatch]

So here is a simple program

import java.util.Random;

class main {

    public static void main(String[] args) {

        int MAX_VALUE = 5_000_000;
        long startTime = System.currentTimeMillis();

        Random rand = new Random();
        for (int i = 0; i < MAX_VALUE; i++) {
            eulerDistance(rand.nextInt(),rand.nextInt(),rand.nextInt(),rand.nextInt());
        }

        long endTime = System.currentTimeMillis() - startTime;

        System.out.print("Time takes: " + endTime);
    }

    static int eulerDistance(int x1, int x2, int y1, int y2) {

        return (int) Math.sqrt(
                Math.pow(((double) x2 - (double) x1), 2) +
                        Math.pow(((double) y2 - (double) y1), 2)
        );
    }


}

I just wanted to test Java vs Go speed running this, for 5 mil iterations java appx takes 0.5 seconds where as go 2-3 seconds and for 50 mil java is 2-3 seconds and didn't wait for go... was taking too long.... I know about java's JIT and have seen it speed things up but what is happening here ?? Its it skipping iterations as there is no use for the value or is it some super optimal code running ?

[tiny solstice]

Detected code, here are some useful tools:

<@&987246717831381062> please have a look, thanks.

[pale tinsel]

5 million is nothing and your program isn't even really optimized, you are calculating the time it takes to run nextInt

and well

there is a chance that java just discarded the call because the result is never used

also it's hard to tell if we can't see go code

[tribal hatch]

Ik, but both langs have exact same code

That's why

[pale tinsel]

show it

[tribal hatch]

I know it can be written much better

package main

import (
    // "example/hello/service"
    "fmt"
    "math"
    "math/rand/v2"
    "time"
)

var globalVariable int = 20

func main() {

    var maxValue int = 5_000_0000

    var startTime int64 = time.Now().UnixMilli()

    for i := 0; i < maxValue; i++ {
        eulerDisntace(rand.Int(), rand.Int(), rand.Int(), rand.Int())
    }

    var endTime int64 = time.Now().UnixMilli() - startTime

    fmt.Printf("Time take to run: %d", endTime)

}

func eulerDisntace(x1 int, x2 int, y1 int, y2 int) int {
    return int(math.Sqrt(math.Pow(float64(x2-x1), 2) + math.Pow(float64(y2-y1), 2)))
}

[tiny solstice]

Detected code, here are some useful tools:

Formatted code

package mainimport (// "example/hello/service"
"fmt""math""math/rand/v2""time") var globalVariableint  = 20func main() {
  var maxValueint  = 5_000_0000var startTimeint 64 = time.Now().UnixMilli() for i :  = 0;


  i < maxValue;
  i++{
    eulerDisntace(rand.Int(), rand.Int(), rand.Int(), rand.Int()) }
  var endTimeint 64 = time.Now().UnixMilli() - startTime fmt.Printf("Time take to run: %d", endTime) }
func eulerDisntace(x1int , x2int , y1int , y2int ) int {
  return int (math.Sqrt(math.Pow(float 64(x2 - x1), 2) + math.Pow(float 64(y2 - y1), 2))) }

[eternal geode]

IIRC Go prioritized predictable latency over throughoutput, its usually much slower in many workloads
But for your case its probably fake timings.

[tribal hatch]

Fake timings ?

[quasi willow]

If no side-effects are observed from calling eulerDistance(...) JIT might decide to eliminate the call entirely

[calm canopy]

save the result of the distance and print it at the end

[quasi willow]

If the content of the loop was more predictable, you would want a sum of the distances to avoid it just finding a shortcut to computing the last one.

[tribal hatch]

Ok will sum it

[stuck frigate]

Any news?

[sand arrow]

i dont know, but try -XX:+PrintCompilation when you launch the program

[civic root]

It is as others have said, the JIT elides the call to eulerDistance as it's return value is not held AND no state is changed in those pure functions Math.sqrt and Math.pow. rand.nextInt()'s are likely called because a seed value is updated each time for the rand object and that's the bulk of your time.

Also, timing this way is prone to error.

Only way to tell is to print compilation AFTER the JIT is warmed.

[calm canopy]

use jmh btw

it is made for this