[Omp] Threadprivate variables and nested parallelism

[James Beyer]

Ok, I am confused.  If you want all of the threads to share the same 
data why is it in the threadprivate list?  Or are you talking about 
nested parallelism where the outer parallel region has the data in 
threadprivate and the inner parallel region has the data shared?  If 
this is the case I don't see why there would be a problem with this.  Of 
course I may change my opinion as I begin bringing full support for 
nested parallelism on line in our compiler.

james

Dieter an Mey wrote:
> Well, you now, Larry, that we are happily profiting from nested 
> parallelism, where tasks would not be the right solution.
>
> And providing copies of large chunks of data for all threads of the 
> inner teams can be a waste of memory...
>
> But I understand that implementing the feature to share threadprivate 
> data may be painful - but I am just a stupid user ...
>
> Dieter
>
>
> Marina Kraeva schrieb:
>> Dieter and Lawrence,
>>
>> Thank you for the clarification.
>>
>> Lawrence, I feel your pain :)
>>
>> Marina.
>>
>> Meadows, Lawrence F wrote:
>>
>>>  
>>> Dieter, I'm sure that your interpretation is correct. Every
>>> thread gets its own copy.
>>>
>>> So if it is "unfortunate" then you would want to be able to
>>> make a threadprivate variable shared in an inner team (using
>>> an explicit shared clause on the parallel directive, I
>>> assume). I have no idea how hard this would be to implement
>>> and I don't like it.
>>>
>>> I wish we could just drop nested parallelism... and threads...
>>>
>>> -----Original Message-----
>>> From: omp-bounces at openmp.org [mailto:omp-bounces at openmp.org] On Behalf
>>> Of Dieter an Mey
>>> Sent: Tuesday, December 12, 2006 9:31 AM
>>> To: Marina Kraeva
>>> Cc: omp at openmp.org
>>> Subject: Re: [Omp] Threadprivate variables and nested parallelism
>>>
>>> My understanding is that all threads will get there own copy - even 
>>> threads of the inner team (unfortunately).
>>>
>>> Dieter
>>>
>>> Marina Kraeva schrieb:
>>>
>>>> Hello,
>>>>
>>>> I could not find in API 2.5 what will happen if a threadprivate
>>>
>>> variable
>>>> is referenced within a nested parallel region, other than this:
>>>>
>>>> The values of data in the threadprivate objects of threads other 
>>>> than the initial thread are guaranteed to persist between two 
>>>> consecutive active parallel regions only if all the following 
>>>> conditions hold:
>>>> * Neither parallel region is nested inside another parallel region.
>>>>
>>>>
>>>> I would think that each thread of the initial team (created for the 
>>>> nesting parallel region) will create a new team, and the threadprivate
>>>
>>>
>>>> copy of this thread will become shared among threads in the new team
>>>
>>> in
>>>> the nested parallel region (so there will be NT shared variables,
>>>
>>> where
>>>> NT is the number of threads in the nesting parallel region).
>>>>
>>>> Am I correct assuming this? Can I count on this behavior or it's
>>>
>>> undefined?
>>>
>>>> Thank you,
>>>> Marina Kraeva.
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>>>>
>>>
>>>
>>
>