Path: csiph.com!usenet.pasdenom.info!news.albasani.net!.POSTED!not-for-mail
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: Mon, 23 Jul 2012 12:17:46 +0200
Organization: albasani.net
Lines: 44
Message-ID: <juj8ca$ges$1@news.albasani.net>
References: <juht3o$a3a$1@news.albasani.net> <ba6e5833-f9a2-428e-815b-aad0ebdf3c55@s6g2000pbi.googlegroups.com> <jui2a3$a3a$2@news.albasani.net> <jui4cg$d5a$1@speranza.aioe.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
X-Trace: news.albasani.net Hxpjf1liurg9gunfaMSLzZM4eRdYLagomgiXDRBycK8OfF+9paN4JcwcVJ+yG7qhqPh3C+OSFXunGYlimKAYNVVhrTGHbk8CByCJipMIyBkRkduCUpIkTPsjgl0bvE8x
NNTP-Posting-Date: Mon, 23 Jul 2012 10:17:46 +0000 (UTC)
Injection-Info: news.albasani.net; logging-data="FGtVFaxwTub+LhEUOhDGO1R94RMkPASindagGu17qpWlqNVHuSZaN0jgaZ9M/6M/yygV7BNKzXHNAoNQiALkvrw3zaSdC38hTEQzQqhJqEOAJTRQXLNZkH4wytk7EGRf"; mail-complaints-to="abuse@albasani.net"
X-Newsreader: Claws Mail 3.8.0 (GTK+ 2.24.10; x86_64-pc-linux-gnu)
Cancel-Lock: sha1:XM+muj4qkP1v7B9AbRwUYBRph+A=
Xref: csiph.com comp.lang.c++:17195 comp.programming.threads:966

On Mon, 23 Jul 2012 02:03:28 +0200
Luca Risolia <luca.risolia@studio.unibo.it> wrote:

> On 23/07/2012 01:28, Melzzzzz wrote:
> > 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.
> 
> A lock-free "BlockingQueue" would probably be more efficient.
> You can also try to implement your Queue with std::array instead of 
> std::deque and see how it performs.

I will try. Seems that java ArrayBlockingQueue is more efficient
because if that. 

> 
> In the C++ version change:
> 
> 	while (queue_.size() >= capacity_)c_full_.wait(lock);
> with
> 	c_full_.wait(lock, [this]{return queue_.size() < capacity_;});
> 
> and
> 	while (queue_.empty())c_empty_.wait(lock);
> with
> 	c_empty_.wait(lock, [this]{return !queue_.empty();});
> 
> Also use a std::lock_guard in empty() instead of std::unique_lock.
> The former is faster.

Yes, I got speed up of few seconds, thanks.

> 
> (On a side note, the C++ version you have given does not have the
> best possible interface for a thread-safe queue)

I have just copied Java BlockingQueue interface, which is of course
suited for Java. Don't know actually how ideal interface would look
like.


>