Hey aikarele

I've seen your 64k demo (varhaiset_signaalit) several months ago and was really impressed. It was the first demo I've seen wich was written in Java and it was able to run in fullscreen (I hadn't known that it's possible before).

Without your demo I won't be here. Thank you for bringing me back to this wonderful language

Gonna update my VM in some hours. I'll drop the results (win98se) here.

Not to knock the demo, but this was possibly in java about a year ago (albeit buggy in the first 1.4 VMs). There was lots of experimentation and apps using it from people on the forum.

Is this a new timer? I would have thought it would be easier to move across the high res timer from j3d. Maybe its just a different wrapper around the same native code..

Hi

first message on this board glad i can post something usefull:

Here's my Timing class (note the cast):

//------------------------------------------------------
import sun.misc.Perf;

public class PerfTimer {
     Perf hiResTimer;
     long freq;
     
     public PerfTimer() {
           hiResTimer = Perf.getPerf();
           freq = hiResTimer.highResFrequency();
     }
     
     public double getTime() {
           return (double)hiResTimer.highResCounter() * 1000 / (double)freq;
     }
}

//------------------------------------------------------


This is the Testing class:

//------------------------------------------------------
public class Test {
     public static void main(String[] args) {
           PerfTimer t = new PerfTimer();
           double start, end, delta, sumOfDeltas, averagedelta;
           int resTestIterations = 1000;
           
           System.out.println("Test1: measure a system-timed intervall");
           start = t.getTime();
           long sysstart = System.currentTimeMillis();
           long sysend;
           do { sysend = System.currentTimeMillis(); }
           while ( sysend < sysstart + 1000);
           end = t.getTime();
           long sysdelta = sysend-sysstart;
           delta = end-start;
           
           System.out.println("systimer-delta: "+sysdelta);
           System.out.println("perftimer-delta: "+delta);
           
           System.out.println("\nTest2: resolution");
           sumOfDeltas = 0;
           for (int i=0;i<resTestIterations;i++) {
                 start = t.getTime();
                 while (start == t.getTime());
                 end = t.getTime();
                 delta = end-start;
                 sumOfDeltas += delta;
           }
           averagedelta = sumOfDeltas/resTestIterations;
           System.out.println("resolution: "+ delta);
           System.out.println("average resolution:"+ averagedelta);
           
           
           System.out.println("\nTest3: measure a perf-timed intervall with sys-timer");
           sysstart = System.currentTimeMillis();
           start = t.getTime();
           do end = t.getTime();
           while (end <start+1000);
           sysend = System.currentTimeMillis();
           delta = end-start;
           sysdelta = sysend-sysstart;
           System.out.println("Perf-delta:"+delta);
           System.out.println("system-Time-delta:"+sysdelta);
     }
}
//------------------------------------------------------


its quite long but i couldn't believe the results first

this is an example output (using Win98se)

Test1: measure a system-timed intervall
systimer-delta: 1040
perftimer-delta: 1002.6182135134682

Test2: resolution
resolution: 0.011733351212569687
average resolution:0.013178229604925037

Test3: measure a perf-timed intervall with sys-timer
Perf-delta:1000.3126100001673
system-Time-delta:980

so this timer actually seems to have ~12E-6 second resolution (is that 12 nanos in english or 12mycro?)

the differences between perf and sys timing are always inside the 50ms-accuracy of the system-timer.

the average resolution goes up and down a bit betweend differnt tests but usually just around 0.002 millis.

lets hope sun has a heart for gamers and leaves this timer!

Hey how did you save you images for the demo?

Using a slight different test on my 3.06GHz XP machine I obtained the following

HiRes counter frequency: 3.0496E9
Mean counter call: 628.34E-9s

On dual processor machines the Windows QueryPerformanceCounter api uses the processor clock counter. This could lead to unexpected results when the processor slows down due to overheating.

---

import sun.misc.Perf;
import java.text.DecimalFormat;

class TestPerformance
{
      public static void main(String[] args)
      {
            Perf p = Perf.getPerf();
            long freq = p.highResFrequency();
            DecimalFormat engFormat = new DecimalFormat("##0.##E0");
            System.out.println("HiRes counter frequency: "+engFormat.format(freq));
            System.out.println("Performance class: "+p.getClass());
            
            for (int i=1; i<20; i++)
            {
                  int n=500;
                  long t=0;
                  for (int j=0; j<n; j++)
                  {
                        long t0=p.highResCounter();
                        t += p.highResCounter()-t0;
                  }
                  System.out.println("Mean counter call: "+engFormat.format(t/(n*(float)freq))+"s");
            }
      }
}

Yep, if you use the hires timer, you definitely need a fallback in case it is not available. But I think it would be nicer if the availability of the hires timer is checked by the Timer class itself, not the caller. For example, the code could be something like this:



Then the caller could use the Timer like this:

Tricky? Because you need a Java version that supports hires timer (i.e.  J2SE 1.4.2 at the moment) to compile it? Why on earth would you have hires fallback timer if you are not using such a compiler?  

Besides, your code will not compile with any Java version because "import sun.misc.Perf;" is missing  

[edit: sorry, of course your code will compile without the import unless the hires timer is needed]

I believe this functionality is committed for 1.5
I suspect this is an early version to get the bugs out.

If its released as part of the 1.5 fromal release it will have a real (not Sun specific) package name.

JK