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Re: Getter performance

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On 10/15/2011 5:59 PM, Aéris wrote:
> Le 15/10/2011 23:36, Arne Vajhøj a écrit :
>> Wrong approach. Write nice clean code. If it is fast enough then
>> fine. If not then measure where the bottleneck is. It seems highly
>> unlikely to be in getters.
>
> I agree with you, my code is clean and fast enough for the moment but
> this question of getter is more general and nag me since few time

If this is for fun, then it is OK. 25 years ago I spent a lot
of time trying to optimize Sieve of Eratosthenes in VAX
assembler. Fun.

But this is work, then stop wasting your employers money and
focus on real problems.

>> First thing would be to run a lot more than 100000 times. Such
>> small intervals will be very random on a multi tasking OS.
>
> Tested on Integer.MAX_VALUE, same result.
>
> But I notice that if I read « tmp » value, results are differents.
> Adding
> 	if (tmp.isEmpty()) {
> 		System.out.println("Empty");
> 	}
> leads to more expected result :
> 	Direct access : 106 ms
> 	Getter call : 2223 ms
> Seems Java compiler is very efficient and don't really call the getter
> if the return value is not read and the getter has no side-effect.

The JIT compiler can do many things.

Another problem with microbenchmarks is that they typical
measure scenario  X1 vs Y1 and there are no guarantee that
X1 faster than Y1 implies that sum(Wi*Xi) is faster
that sum(Wi*Yi) for i=1..n, which is the real world.

Small differences can mean a lot of difference for a
single scenario, which is not relevant for the real world
with hundreds or thousands of almost identical but still
different scenarios.

Arne

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Getter performance Aéris <aeris@imirhil.fr> - 2011-10-15 23:03 +0200
  Re: Getter performance Arne Vajhøj <arne@vajhoej.dk> - 2011-10-15 17:36 -0400
    Re: Getter performance Arne Vajhøj <arne@vajhoej.dk> - 2011-10-15 17:42 -0400
      Re: Getter performance BGB <cr88192@hotmail.com> - 2011-10-15 15:00 -0700
        Re: Getter performance markspace <-@.> - 2011-10-15 15:20 -0700
          Re: Getter performance David Lamb <dalamb@cs.queensu.ca> - 2011-10-20 12:45 -0400
            Re: Getter performance Roedy Green <see_website@mindprod.com.invalid> - 2011-10-21 14:27 -0700
              Re: Getter performance Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2011-10-21 18:57 -0700
                Re: Getter performance Patricia Shanahan <pats@acm.org> - 2011-10-22 07:27 +0100
                Re: Getter performance Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-10-22 09:57 -0300
              Re: Getter performance Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-21 22:12 -0400
    Re: Getter performance Aéris <aeris@imirhil.fr> - 2011-10-15 23:59 +0200
      Re: Getter performance Arne Vajhøj <arne@vajhoej.dk> - 2011-10-15 19:44 -0400
        Re: Getter performance Aéris <aeris@imirhil.fr> - 2011-10-16 13:14 +0200
          Re: Getter performance Lars Enderin <lars.enderin@telia.com> - 2011-10-16 16:28 +0200
  Re: Getter performance Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-16 09:47 -0400
  Re: Getter performance Jaap Droogers <JaapDroogers@unusable.meel.homelinux.net> - 2011-10-16 22:12 +0200
    Re: Getter performance BGB <cr88192@hotmail.com> - 2011-10-16 13:58 -0700
    Re: Getter performance David Lamb <dalamb@cs.queensu.ca> - 2011-10-20 12:51 -0400
      Re: Getter performance Paul Cager <paul.cager@googlemail.com> - 2011-10-21 08:49 -0700
  Re: Getter performance Roedy Green <see_website@mindprod.com.invalid> - 2011-10-21 08:02 -0700
  Re: Getter performance Wanja Gayk <brixomatic@yahoo.com> - 2011-10-22 21:11 +0200

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