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<p class="MsoNormal"><span lang="EN-US">Hi everyone,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thank you for allowing me to join this mailing list.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">My name is Ken Fogel and I was a Computer Science instructor at Dawson College in Montreal for 31 years, having retired 3 years ago. I was chairperson for 25 of those years and led the change from COBOL to Java in 2000.
I am a Java Champion and organize, with fellow JCs, the JChampions Conference. I also sit on the JCP Executive Committee. Like all retired academics I wrote a book entitle Transitioning to Java from Packt for devs who need to move to Java from any other language.
Finally, I still get to present at conferences, and it is work I am doing with the JMH for JavaLand that has led me to this mailing list.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Some years ago, I wrote a program that demonstrated the relative differences between the various collection in Java. The program worked as required, made for a good lecture, and proved why no one should use a LinkedList
(this remark is meant to be funny and true). A little over a year ago I discovered the jmh and created a version of my program using it. Unfortunately, I could not run the benchmarks as I did in my version as the results were presented in a Swing table but
that is not the issue I am having. Here is the measurement code for adding an element at the end of an ArrayList from my pre-jmh code:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">for (int y = 0; y < REPETITIONS; ++y) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> arrayDeque = new ArrayDeque<>();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> for (int x = 0; x < SIZE; ++x) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> arrayDeque.add(dataArray[x]);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> startTime = System.nanoTime();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> arrayDeque.addFirst("Dawson College");<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> endTime = System.nanoTime() - startTime;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> runningTotal += endTime;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The dataArray is a simple array of 10000 strings. I use the same set of words for every test. This worked well enough. The actual time to insert was calculated after a new ArrayList was created and populated for every
repetition. This was necessary because had I created a new copy with :<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">arrayDeque = new ArrayDeque<>(Arrays.asList(dataArray));<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I end up with an ArrayDeques that is the same size as the Array I am initializing it with. The problem is that this ArrayDeque has no slack space so it must immediately grow, As I am interested in the performance when
there is slack space, I create the ArrayDeque in a loop. This results in the ArrayDeque having slack space.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">When I moved to the jmh I could not find a way to create and initialize the ArrayList as @Benchmark timed the entire method’s code. I thought I figured it out by using an inner static class annotated with @State. It
did not work. I discovered that the ArrayList was being initialized for each iteration but, and this was a very big but, I discovered after reading numerous StackOverflows and then looking at the jmh source code that iterations that were not set to “Mode.SingleShotTime”
executed the @Benchmark method a random number of times per iteration. This would be fine except that the @State class/method was only invoked once per iteration and not every time the method was executed as I required.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">If you have read this far you can probably guess my question. Is it possible to execute code that is part of a @Benchmark method but that is not included in the timing. Is there or could there be an annotation for this
rather than use SingleShotTime and then have a large value for measurementIterations . Something like:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">@Benchmark<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">public void do10InsertLastElementArrayList(Blackhole blackhole) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-US"> @IgnoreOn<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span lang="EN-US"> Deque <String> arrayDeque = new ArrayDeque<>();<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span lang="EN-US"> for (int x = 0; x < SIZE; ++x) {<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span lang="EN-US"> arrayDeque.add(dataArray[x]);<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span lang="EN-US"> }<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span lang="EN-US"> @IgnoreOff<o:p></o:p></span></b></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> arrayDeque.add("Dawson College");<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> blackhole.consume(arrayDeque); // Not certain I need this<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">If the operation does not mutate anything then there is no issue. It is when I mutate something that I need to restore the state of variables to before the mutation every time and not have this included in the timing
measurement.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thank you for your patience in reading this and for any assistance you can provide.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Ken<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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