Re: Atomic thread safe integer increment..

From:

Thomas Hawtin <usenet@tackline.plus.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 14 Sep 2006 14:04:44 +0100

Message-ID:

<45095375$0$569$ed2619ec@ptn-nntp-reader03.plus.net>

Thomas Kellerer wrote:

On 14.09.2006 14:04 lordy wrote:

Hi, I want to keep a running 'int' total across threads but without the
'synchronized' overhead. (This total will be spinning pretty fast).

I guess the most performant(?) option is to maintain separate totals and
combine them at report time?

The perfomance "penalty" of a synchronized block is relatively small.

I think there is an article on DeveloperWorks that de-mystifies the
common believe that synchronize will make things slower. If I recall the
article correctly this was true for JDK up to 1.3 but starting with 1.4
(or 1.5 not 100% sure about that) the overhead is so small that it does
not justify the effort to avoid it.

If it's a contended lock, particularly on a multicore machine, it could
well be a problem. Having said that, in this case the lock shouldn't be
held for very long.

A local value for each thread should be much faster. Alternatively, if
you can live with an inaccurate variable, just use volatile (I think
that works in 1.4).

Tom Hawtin
--
Unemployed English Java programmer
http://jroller.com/page/tackline/