Hi Isaac,

I've added "dynamic" in the text, as you advised. Good point.

Regarding your comments #2 and #4 -- I don't care what Python, Java, PHP or any of the other languages are doing while I want them to do a task with "loops, dynamic arrays with numbers, basic math operations". The idea is to compare exactly this overhead and efficiency.

I've already commented #3 -- you are right, but I don't have the time to update this, and frankly since Java and Python/PHP/Perl are different kind of languages, I think that we may leave that as-is. Write a comment about this at the blog, and I'll reply the same, so that we have a public log of this.

Regarding #5 -- I don't really understand what you mean here. I test the default languages setup. I have no idea what the size of a Python/Perl/PHP/Java list is. And I won't tweak any of the implementations by optimizing them for the current task/algorithm. This is a general test, not a try to complete a task in the fastest possible way for each programming language.

Cheers.
--Ivan

On 20.6.2012 г. 20:59 ч., Isaac Gouy wrote:

Hi Ivan

I'm testing "loops, arrays with numbers, basic math operations".

1) Please change your blog post to say what you've told me you want to test -- not "arrays with numbers" -- but "lists with numbers" or "resizable arrays with numbers" or "dynamic arrays with numbers".


2) You assume that you're mainly testing - loops, resizabe arrays with numbers, basic math operations - but do you know whether that actually is what you're testing for each of those programs?

When I profile your Java program, I find that 58% of the total time is spent on garbage collection -- not loops, not lists with numbers, not basic math operations.

$ java -Xprof PrimeNumbersBenchmarkApp

58% of the total time is spent on garbage collection and growing the heap, because the initial heap size has not been set appropriately.

Regarding the special function -- you are right. ... How does this make Java slower?

3) Does it make your Java program relatively slower compared to your Python program?

"... you can work around the problem by moving the body of main to a new
method and calling it once from main to give the compiler a chance to compile
the code".

That's exactly what I've done, so I don't think I'm violating
any Java recommendations here.

4) That's what you think you've done but -Xprof shows 18.5% of the calls were interpreted.

Look, I'm not biased towards Java or any other language -- I don't even
program in Java *or* Python. ... I don't know what your idea here is ...

5) The idea is to help you understand that you aren't comparing what you say you're comparing.

If your intention is to compare time taken to grow a list, then shouldn't you start with lists that are the same size, and start with program heap that's the same size, and use the same max heap size?

user+sys for your Java program = 20.56s

But change
         ArrayList<Integer> s = new ArrayList<Integer>();
to
         ArrayList<Integer> s = new ArrayList<Integer>(8192);
and run with

         java -Xms1G PrimeNumbersBenchmarkApp

user+sys  = 6.9s

I don't think you're comparing what you say your're comparing.

P.S. You are not answering all my questions -- System.nanoTime() is returning
the wall-clock time? If yes, how are you sure that the compiler isn't
executing something on more than one core (for example running the loop on one
core, and doing garbage collection on the other).

I expect that the JVM is running GC on a different core if possible. Those wall-clock times were for comparison of the first run of the Java program with the second run of the Java program, with the third run of the Java program. Not for comparison of the Java program with the Python program.

best wishes, Isaac