[Cython] prange CEP updated

[Dag Sverre Seljebotn]

On 05/04/2011 01:48 PM, mark florisson wrote:
> On 4 May 2011 13:47, mark florisson<markflorisson88 at gmail.com>  wrote:
>> On 4 May 2011 13:45, Dag Sverre Seljebotn<d.s.seljebotn at astro.uio.no>  wrote:

>>> Look.
>>>
>>> i = 42
>>> for i in prange(n):
>>>     f(i)
>>> print i # want 42 whenever n == 0
>>>
>>> Now, translate this to:
>>>
>>> i = 42;
>>> #pragma omp parallel for firstprivate(i) lastprivate(i)
>>> for (temp = 0; ...; ...) {
>>>     i = ...
>>> }
>>> #pragma omp parallel end
>>> /* At this point, i == 42 if n == 0 */
>>>
>>> Am I missing something?
>>
>> Yes, 'i' may be uninitialized with nsteps>  0 (this should be valid
>> code). So if nsteps>  0, we need to initialize 'i' to something to get
>> correct behaviour with firstprivate.

This I don't see. I think I need to be spoon-fed on this one.

>   And of course, if you initialize 'i' unconditionally, you change 'i'
> whereas you might have to leave it unaffected.

This I see.

Dag Sverre