Re: Why is java consumer/producer so much faster than C++

From	Melzzzzz <mel@zzzzz.com>
Newsgroups	comp.lang.c++, comp.programming.threads
Subject	Re: Why is java consumer/producer so much faster than C++
Date	2012-07-23 01:28 +0200
Organization	albasani.net
Message-ID	<jui2a3$a3a$2@news.albasani.net> (permalink)
References	<juht3o$a3a$1@news.albasani.net> <ba6e5833-f9a2-428e-815b-aad0ebdf3c55@s6g2000pbi.googlegroups.com>

Cross-posted to 2 groups.

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On Sun, 22 Jul 2012 15:42:55 -0700 (PDT)
Joshua Maurice <joshuamaurice@gmail.com> wrote:

> 
> 
> What g++ optimization options did you use? If you didn't compile with
> proper optimization flags (e.g. at least -O2), then the numbers you
> have are meaningless.

I have used -O2.

> 
> Also, you might be testing the difference between std::rand() and
> Java's Random.

Possibly.

> 
> Also, why did you use dynamic allocation in the C++ code for an int?

Actually with non dynamical allocation seems to be slower ;)

> If your original goal was to compare the Java way to the C++ way, you
> are not doing it right. This is especially troubling after you
> apparently went through the effort to make the queue support move-only
> types. (Not sure. I'm still new to move-semantics.)

That was necessary in order to put unique_ptr in queue.

> 
> Also,
> >         std::unique_ptr<int> arr[size];
> ...
> >             arr[std::rand()%size] = produced.take();
> I wonder if it's possible to optimize that into a simple assignment,
> or whether there will be a call to delete() - or at least a branch to
> test if the internal member pointer is null.

I have removed that statement , removed called to rand, left 
only take, made int's non dynamic
and I got following time:

bmaxa@maxa:~/examples$ g++ -Wall -O2 -pthread -std=c++0x consprod1.cpp -o consprod1
consprod1.cpp: In lambda function:
consprod1.cpp:58:19: warning: unused variable ‘size’ [-Wunused-variable]
bmaxa@maxa:~/examples$ time ./consprod1

real	0m23.335s
user	0m22.177s
sys	0m16.417s

with java, I have removed rand too...
bmaxa@maxa:~/examples$ javac consprod.java
bmaxa@maxa:~/examples$ time java consprod

real	0m12.491s
user	0m21.001s
sys	0m0.524s

Still twice as fast as c++.
What it looks like, is that c++ spends much more time in syscalls
(futex) than java and that explains big difference.

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Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-22 23:59 +0200
  Re: Why is java consumer/producer so much faster than C++ Joshua Maurice <joshuamaurice@gmail.com> - 2012-07-22 15:42 -0700
    Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-23 01:28 +0200
      Re: Why is java consumer/producer so much faster than C++ Luca Risolia <luca.risolia@studio.unibo.it> - 2012-07-23 02:03 +0200
        Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-23 12:17 +0200
          Re: Why is java consumer/producer so much faster than C++ Luca Risolia <luca.risolia@studio.unibo.it> - 2012-07-24 00:33 +0200
            Re: Why is java consumer/producer so much faster than C++ Bo Persson <bop@gmb.dk> - 2012-07-24 19:50 +0200
  Re: Why is java consumer/producer so much faster than C++ Juha Nieminen <nospam@thanks.invalid> - 2012-07-23 06:37 +0000
    Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-23 12:33 +0200
      Re: Why is java consumer/producer so much faster than C++ Juha Nieminen <nospam@thanks.invalid> - 2012-07-23 11:46 +0000
        Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-23 15:33 +0200
  Re: Why is java consumer/producer so much faster than C++ Zoltan Juhasz <zoltan.juhasz@gmail.com> - 2012-07-23 06:57 -0700
    Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-23 18:42 +0200
      Re: Why is java consumer/producer so much faster than C++ Howard Hinnant <howard.hinnant@gmail.com> - 2012-07-23 13:23 -0700
        Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-24 00:32 +0200
          Re: Why is java consumer/producer so much faster than C++ Howard Hinnant <howard.hinnant@gmail.com> - 2012-07-23 18:11 -0700
            Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-24 11:21 +0200
            Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-24 21:45 +0200
              Re: Why is java consumer/producer so much faster than C++ Luca Risolia <luca.risolia@studio.unibo.it> - 2012-07-24 23:24 +0200
                Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-25 00:48 +0200
                Re: Why is java consumer/producer so much faster than C++ Luca Risolia <luca.risolia@studio.unibo.it> - 2012-07-25 01:21 +0200
              Re: Why is java consumer/producer so much faster than C++ Howard Hinnant <howard.hinnant@gmail.com> - 2012-07-24 17:35 -0700
              Re: Why is java consumer/producer so much faster than C++ Luca Risolia <luca.risolia@studio.unibo.it> - 2012-07-26 21:19 +0200
                Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-26 21:56 +0200
                Re: Why is java consumer/producer so much faster than C++ Luca Risolia <luca.risolia@studio.unibo.it> - 2012-07-26 22:15 +0200
                Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-26 23:01 +0200
                Re: Why is java consumer/producer so much faster than C++ Luca Risolia <luca.risolia@studio.unibo.it> - 2012-07-26 23:12 +0200
                Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-27 00:24 +0200
                Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-27 00:48 +0200
                Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-27 05:43 +0200
                Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-27 07:43 +0200
                Re: Why is java consumer/producer so much faster than C++ Marc <marc.glisse@gmail.com> - 2012-07-26 21:10 +0000
                Re: Why is java consumer/producer so much faster than C++ Donkey Hottie <donkey@fredriksson.dy.fi> - 2012-07-27 01:05 +0300
                Re: Why is java consumer/producer so much faster than C++ Paavo Helde <myfirstname@osa.pri.ee> - 2012-07-26 17:12 -0500
        Re: Why is java consumer/producer so much faster than C++ yatremblay@bel1lin202.(none) (Yannick Tremblay) - 2012-07-24 12:51 +0000
          Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-24 17:47 +0200
            Re: Why is java consumer/producer so much faster than C++ yatremblay@bel1lin202.(none) (Yannick Tremblay) - 2012-07-25 08:09 +0000
              Re: Why is java consumer/producer so much faster than C++ Howard Hinnant <howard.hinnant@gmail.com> - 2012-07-25 08:46 -0700
  Re: Why is java consumer/producer so much faster than C++ Dombo <dombo@disposable.invalid> - 2012-07-23 22:57 +0200
    Re: Why is java consumer/producer so much faster than C++ Joshua Maurice <joshuamaurice@gmail.com> - 2012-07-23 21:54 -0700
      Re: Why is java consumer/producer so much faster than C++ Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-07-24 12:50 +0000
  Re: Why is java consumer/producer so much faster than C++ James Kanze <james.kanze@gmail.com> - 2012-07-29 03:27 -0700
    Re: Why is java consumer/producer so much faster than C++ Melzzzzz <mel@zzzzz.com> - 2012-07-29 14:40 +0200
  Re: Why is java consumer/producer so much faster than C++ Ricardo Nabinger Sanchez <rnsanchez@wait4.org> - 2012-08-14 22:48 +0000

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