[Omp] First Touch Inicialization

[Patricia Bittencourt Sampaio]

 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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