Re: How to make this program more efficient?

James Kanze <>
Wed, 24 Sep 2008 01:21:10 -0700 (PDT)
On Sep 24, 1:00 am, Jon Harrop <> wrote:

peter koch wrote:

On 23 Sep., 21:27, Jon Harrop <> wrote: wrote:

You still make a confusion between locks and memory

Sorry: I read "synchronization" and assumed Peter was
referring to locks.

The two are quite different: although Posix (and doubtlessly
Windows as well) guarantees synchronization accross a lock, lock
free algorithms exist, but they still also require

Well - I can speak for myself and did not mean locks -
simply synchronisation.

Are memory barriers a form of synchronization?

On many machines (e.g. Sparc), they're the only form of memory
synchronization. (I think that Intel refers to them as fences.
I think that Intel also offers some additional guarantees, and
that in particular---if I've understood correctly---it
implicitly generates full memory synchronization around an xchg
instruction. I'm more familiar with Sparc: for Sparc, you
should read section 3.2 of the "Sparc Architecture Manual",

James Kanze (GABI Software)
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