Groups > comp.lang.java.programmer > #7423

Re: Style Police (a rant)

From	Lew <lewbloch@gmail.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: Style Police (a rant)
Date	2011-08-27 09:50 -0700
Organization	http://groups.google.com
Message-ID	<36f4953c-f085-4850-85eb-bb248a8cf1bb@glegroupsg2000goo.googlegroups.com> (permalink)
References	(1 earlier) <j3akb0$61g$1@news.albasani.net> <j3akn1$6tu$1@news.albasani.net> <d906c374-1751-4b85-b844-fd82569ea9ac@glegroupsg2000goo.googlegroups.com> <j3b49j$8u6$1@news.albasani.net> <j3b4mn$a2e$1@news.albasani.net>

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Jan Burse wrote:
>> Without the final keyword a JIT potentially needs to reoptimize
>> code, when classes are later loaded. Since although an analysis
>> might yield that a class method is actually not overridden,
>> it might still get overridden at run time.
> 
> Of course the problem is not so much there for JITs that do
> call site specific PICs. So a method that is not overridden
> will also have not multiple entries in the PICs.
> 
> But with the final keyword we can put a closure mark on the
> PICs we don't need to bother of extending them at runtime
> in case a new method implementation pops up at the call site.
> And this could change the realization of the PICs.
> 
> So I guess this is not an urban legend. Unfortunately I did
> document so much my findings that final has an impact. It
> occurs to me once a while. But also I am switching the JDK
> a couples of time, i.e. migrating form 32-bit to 64-bit.
> 
> With the 64-bit I noticed I different sensitivity profile.
> Things that made the 32-bit JDK stumble don't have any impact
> at all for the 64-bit. For example the garbage collection runs
> very smooth with much less effort.
> 
> So not an urban legend but maybe yes a moving target.

Thanks for the information.

Except in performance-critical hot spots in code, such as yours presumably was, the movability of the target militates against such strategies. More importantly, use of 'final' on classes and methods is a semantic restriction; you have to be responsible for the consequences to program logic. Fortunately for your use case, it's frequently the right thing to do.

As usual, the rule is to do the right thing for the logic first and foremost. The problem with your post on the optimization aspect is that it reads like a general rule when in fact it was a particular case for a particular environment with a (presumably) important effect on (presumably) critical performance.  By your post cited here, it isn't even a durable effect.  Again, the downside is mitigated by the likely semantic benefit of using 'final' in that context, but that seems more coincidental in this case than deliberate.

I notice that you didn't describe your performance-test methodology.  HotSpot compilation has some interesting variation in its effects depending on run-time considerations like whether you've heated up the analyzer (run through the code x thousand times), other things in the JVM, changes in the underlying platform, brand of JVM (strictly speaking only Oracle's has "HotSpot"), and so on.  In your case I'll presume your methodology was rigorous enough, although "Unfortunately I did document so much my findings that final has an impact" should make anyone nervous about that.  But that does not mean that one should recommend 'final' as a way to encourage inlining as a general technique, particularly in the face of the many expert warnings against that very practice.

-- 
Lew

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Thread

Style Police (a rant) Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-26 20:56 -0400
  Re: Style Police (a rant) Robert Klemme <shortcutter@googlemail.com> - 2011-08-27 09:58 +0200
  Re: Style Police (a rant) Rajiv Gupta <rajiv@invalid.com> - 2011-08-27 18:02 +1000
    Re: Style Police (a rant) v_borchert@despammed.com (Volker Borchert) - 2011-08-27 08:40 +0000
  Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-27 13:27 +0200
    Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-27 13:33 +0200
      Re: Style Police (a rant) Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-27 11:08 -0400
      Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-27 08:34 -0700
        Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-27 08:37 -0700
        Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-27 17:59 +0200
          Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-27 18:06 +0200
            Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-27 18:08 +0200
            Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-27 09:50 -0700
              Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-27 19:15 +0200
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-27 13:09 -0700
                Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-27 23:18 +0200
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-27 16:10 -0700
                Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-28 01:59 +0200
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-27 18:59 -0700
                Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-28 15:32 +0200
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-28 13:09 -0700
                Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-29 04:02 +0200
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-28 19:20 -0700
                Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-29 09:44 +0200
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-29 08:30 -0700
                Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-29 16:37 +0000
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-29 12:10 -0700
                Re: Style Police (a rant) Robert Klemme <shortcutter@googlemail.com> - 2011-08-29 18:21 +0200
                Re: Style Police (a rant) Jan Burse <janburse@fastmail.fm> - 2011-08-29 04:06 +0200
    Re: Style Police (a rant) Wanja Gayk <brixomatic@yahoo.com> - 2011-09-10 06:45 +0200
      Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-09-10 11:40 +0000
        Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-09-10 14:06 -0700
          Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-09-11 14:07 +0000
            Re: Style Police (a rant) Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 10:55 -0400
              Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-09-11 23:34 +0000
            Re: Style Police (a rant) Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 10:58 -0400
              Re: Style Police (a rant) Patricia Shanahan <pats@acm.org> - 2011-09-11 10:12 -0700
            Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-09-11 09:47 -0700
              Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-09-11 23:32 +0000
            Re: Style Police (a rant) Wanja Gayk <brixomatic@yahoo.com> - 2011-09-11 21:20 +0200
              Re: Style Police (a rant) Cthun <cthun_117@qmail.net.au> - 2011-09-11 17:11 -0400
                Re: Style Police (a rant) Wanja Gayk <brixomatic@yahoo.com> - 2011-09-12 01:22 +0200
                Re: Style Police (a rant) Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 21:13 -0400
                Re: Style Police (a rant) Retahiv Oopsiscame <roopsisc@gmail.com> - 2011-09-11 16:54 -0700
                Re: Style Police (a rant) Cthun <cthun_117@qmail.net.au> - 2011-09-11 23:42 -0400
                Re: Style Police (a rant) "Cthun" <cthun_117@qmail.net.au> - 2011-09-12 04:56 -0400
                Re: Style Police (a rant) Cthun <cthun_117@qmail.net.au> - 2011-09-12 05:12 -0400
                Re: Style Police (a rant) "Cthun" <cthun_117@qmail.net.au> - 2011-09-12 04:59 -0400
                Re: Style Police (a rant) Cthun <cthun_117@qmail.net.au> - 2011-09-12 05:13 -0400
              Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-09-11 23:17 +0000
                Re: Style Police (a rant) Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 21:12 -0400
                Re: Style Police (a rant) Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-09-12 07:36 -0300
              Re: Style Police (a rant) "Cthun" <cthun_117@qmail.net.au> - 2011-09-12 04:58 -0400
                Re: Style Police (a rant) Cthun <cthun_117@qmail.net.au> - 2011-09-12 05:12 -0400
        Re: Style Police (a rant) Wanja Gayk <brixomatic@yahoo.com> - 2011-09-11 15:33 +0200
          Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-09-11 09:42 -0700
            Re: Style Police (a rant) Lars Enderin <lars.enderin@telia.com> - 2011-09-11 20:35 +0200
              Re: Style Police (a rant) Retahiv Oopsiscame <roopsisc@gmail.com> - 2011-09-11 16:55 -0700
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-09-11 20:36 -0700
                Re: Style Police (a rant) Lars Enderin <lars.enderin@telia.com> - 2011-09-12 10:05 +0200
                Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-09-12 15:35 -0700
                Re: Style Police (a rant) "Cthun" <cthun_117@qmail.net.au> - 2011-09-12 04:52 -0400
                Re: Style Police (a rant) Cthun <cthun_117@qmail.net.au> - 2011-09-12 05:14 -0400
                Re: Style Police (a rant) "Cthun" <cthun_117@qmail.net.au> - 2011-09-12 06:42 -0400
                Re: Style Police (a rant) Cthun <cthun_117@qmail.net.au> - 2011-09-12 07:20 -0400
                Re: Style Police (a rant) "Cthun" <cthun_117@qmail.net.au> - 2011-09-12 08:46 -0400
              Re: Style Police (a rant) Tom Anderson <twic@urchin.earth.li> - 2011-09-12 20:18 +0100
            Re: Style Police (a rant) Wanja Gayk <brixomatic@yahoo.com> - 2011-09-11 21:20 +0200
              Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-09-11 13:52 -0700
          Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-09-12 00:17 +0000
      Re: Style Police (a rant) Arne Vajhøj <arne@vajhoej.dk> - 2011-09-10 21:32 -0400
        Re: Style Police (a rant) Wanja Gayk <brixomatic@yahoo.com> - 2011-09-11 13:27 +0200
          Re: Style Police (a rant) Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 11:05 -0400
        Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-09-11 13:23 +0000
          Re: Style Police (a rant) Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-11 10:04 -0400
            Re: Style Police (a rant) Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-09-11 12:45 -0300
              Re: Style Police (a rant) Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 16:53 -0400
          Re: Style Police (a rant) Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 10:59 -0400
            Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-09-11 21:25 +0000
  Re: Style Police (a rant) Tom Anderson <twic@urchin.earth.li> - 2011-08-27 14:00 +0100
    Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-27 08:42 -0700
    Re: Style Police (a rant) Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-27 11:58 -0400
  Re: Style Police (a rant) "John B. Matthews" <nospam@nospam.invalid> - 2011-08-28 08:21 -0400
    Re: Style Police (a rant) Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-08-28 18:07 -0300
  Re: Style Police (a rant) Roedy Green <see_website@mindprod.com.invalid> - 2011-08-29 04:20 -0700
  Re: Style Police (a rant) Tim Slattery <Slattery_T@bls.gov> - 2011-08-29 09:11 -0400
    Re: Style Police (a rant) Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-29 20:50 -0400
      Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-30 11:27 +0000
        Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-30 09:36 -0700
          Re: Style Police (a rant) Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-30 17:51 +0000
      Re: Style Police (a rant) Tim Slattery <Slattery_T@bls.gov> - 2011-08-30 08:51 -0400
      Re: Style Police (a rant) Patricia Shanahan <pats@acm.org> - 2011-08-30 09:04 -0700
        Re: Style Police (a rant) Lew <lewbloch@gmail.com> - 2011-08-30 09:43 -0700
          Re: Style Police (a rant) Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-08-31 00:31 +0200

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