Re: Changesets: Re: Parallel access to data created with Octave

[Jarno Rajahalme]

On May 25, 2010, at 2:23 AM, ext Jaroslav Hajek wrote:

> On Tue, May 25, 2010 at 10:55 AM, Michael D. Godfrey
> <address@hidden> wrote:
>> On 5/25/10 8:43 AM, Jaroslav Hajek wrote:
>>> 
>>> Although parts of this work are useful per se, it feels more like a
>>> workaround than a solution. What you really need is a thread-safe
>>> reference-counting.
>>> 
>> 
>> How hard is this to implement?  I seems to me that there will be increasing
>> demand
>> for thread-safe operation and work-arounds are not the way to get there.
>> 
>> Michael
>> 
>> 
> 
> In the simplest setup, counter increments and decrements should be
> decorated by #pragma omp atomic.
> I think we could have a set of macros, similar to Py_INCREF et al, for
> doing this.

Would this use a global lock? That would be rather bad, I think.

GCC 4.1 and above has builtins for atomic increment / decrement 
(__sync_sub_and_fetch () etc.). This site has very good intro to the topic:

http://golubenco.org/2007/06/14/atomic-operations/

Looks pretty straightforward. Apparently ICC implements these too, so it is not 
GCC only.

        Jarno