Re: Atomic thread safe integer increment..
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'm guessing Most processors have some kind of atomic (and hopefully)
thread safe increment command.
However a big of Googling suggests this may be possible in Java 1.5 but
not in Java 1.4.2 ('Twas an IBM article
http://www-128.ibm.com/developerworks/java/library/j-jtp11234/)
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.
....
There is an inherent cost to synchronization in forcing threads to run
serially rather than in parallel, but you would have to be doing a
simple integer increment very, very frequently relative to other work
before that would be a problem.
The usual advice, start simple and optimize if necessary, applies.
Patricia