Re: JDOM2 and Performance.

Tip of the day: http://code.google.com/p/caliper/

</Mattias>

----- Original Message -----
Subject: Re: [jdom-interest] JDOM2 and Performance.
Date: Fri, 14 Oct 2011 10:08:36 +0200
From: Noel Grandin <[email protected]>

Hi

Performance testing on the Java VM is tricky.
To avoid getting caught out by cache-hot/cache-cold and JIT vs. not-JIT 
things, it's preferrable to do something like
this in PerfTest#timeRun(Runnnable)

// warm up the caches and get the JIT going
for (int i=0; i<10; i++) {
runnable.run();
}

// give the JIT time to run, and get GC to run - GC can be stubborn 
sometimes
for (int i=0; i<3; i++) {
Thread.sleep(100);
System.gc();
}

// need 20 runs to get a decent average and standard deviation
ArithmeticMean mean = new ArithmeticMean(); // these two classes are in 
jakarata-commons-math
Variance deviation = new Variance();
for (int i=0; i<20; i++) {
long time1 = System.currentTimeNanos();
runnable.run();
long time2 = System.currentTimeNanos();
mean.increment(time2 - time1);
deviation.increment(time2 - time1);
}

System.out.println("result = " + mean.getMean() + " +- " + 
deviation.getVariance());

Regards, Noel Grandin

Rolf wrote:
 > Hi all.
 >
 > I have put together a 'simple' system for measuring the relative 
performance of JDOM2. The idea is that I need to know
 > whether I am improving or breaking JDOM performance as the code evolves.
 >
 > Currently the metric code is only useful of you compare apples to 
apples, and, in this case, it means processing a
 > single (medium size) XML document on my laptop, yada-yada-yada. But, 
it should be useful as a tool to get a feel for
 > what a code-change does.
 >
 > Already I can see that I probably have an issue in the SAXHandler 
(possibly an issue in JDOM-1.1.2 actually) because
 > 1.1.2 is 5-times faster in that area than JDOM2.
 >
 > I have put together a results page here:
 >
 > http://hunterhacker.github.com/jdom/jdom2/performance.html
 >
 > It also describes what each test does. If you are interested in 
seeing the code and what it does have a look here (it
 > is not well documented and it is still perhaps evolving):
 >
 > 
https://github.com/hunterhacker/jdom/commit/8b719c86913398ace8e197b6de145b33d9d300bb
 >
 >
 > Rolf
 > _______________________________________________
 > To control your jdom-interest membership:
 > http://www.jdom.org/mailman/options/jdom-interest/[email protected]
 >

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   </Mattias>


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