[Omp] First Touch Inicialization

[Shah, Sanjiv]

Not only from compiler to compiler, but also may heavily depend upon the particular test case you have.

Sanjiv

--
Sanjiv, 217-403-4244

-----Original Message-----
From: Omp-bounces at openmp.org [mailto:Omp-bounces at openmp.org] On Behalf Of eric duncan
Sent: Wednesday, March 08, 2006 12:05 PM
To: Patricia Bittencourt Sampaio
Cc: omp at openmp.org
Subject: Re: [Omp] First Touch Inicialization

When making comments like this, it would be helpful if you specified the
type of machine, operating system, and compiler you are using.  I don't
think that this is accurate as a general statement and may well vary
considerably from one compiler version (or machine, or OS, etc) to the next.

Patricia Bittencourt Sampaio wrote On 03/08/06 09:47,:
>  Hello,
> 
>      As an extension of the previus messages related
> to initialization. I've found out recently that when
> threadprivate variables are used on a parallel region 
> it demands a considerable overhead for the
> initialization of these variables. 
>      And besides that, this overhead exists even when
> just one thread is used (when OMP_NUM_THREADS=1). 
>      I have executed a program with a parallel region
> for the initialization, compiling that program with
> and without OpenMP directives. My intend was to verify
> if OpenMP directives generate some overhead. 
>      The directives for Parallel Region does not
> generate overhead, or if it does, it is not
> significant. However for the parallel region that use
> the threadprivate variables, I observe that the
> computation comprised on at took 80 seconds to
> conclude, using just one thread. And executing this
> without openmp directives it took 40 seconds. And
> these values increase on the same proportial (2x) as
> additional processors, always as a potencial of 2, are
> used. 
> 
> regards,
> 
> 
> Patricia Bittencourt Sampaio
> ====================================
> Federal University of Rio de Janeiro
> 
> 
> 
> 		
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