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


From: Jarno Rajahalme
Subject: Re: Changesets: Re: Parallel access to data created with Octave
Date: Tue, 25 May 2010 12:43:29 -0700

For a longer (C++) story, see:

"C++ Atomic Types and Operations"
http://www.open-std.org/JTC1/sc22/wg21/docs/papers/2007/n2427.html

  Jarno

On May 25, 2010, at 12:31 PM, ext Jarno Rajahalme wrote:

> 
> 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
> 
> 




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