Re: Calling a subroutine causes serialization of threads?

Randy,

Thanks for the response! I didn't expect to get any response so quickly
as I thought this is not a popular topic, due to the nature of the
problem.

I am using google's interface and don't know how to quote the posting
automatically in google, so just cut and paste what you posted in
pieces.

1) "Why not inline thomas() into the loop?"
I haven't given it a thought. I'll make it inline, and perhaps by hand.

2) I did turn off the optimization, by specifying -O0 with the
compilers
I used. For intel and Compaq compilers the default is noalias. That
doesn't change things too much.

3) The OpenMP code and the Pthreads code behave pretty much
the same. I suppose the barrier in OpenMP is more efficient than
my hand coded barrier in Pthreads.

4) "Have you dumped the unoptimized assembly of the parallel region to
see"
No, I haven't. I'll do that, and perhaps will post the trimed
comparison here
if not too long...

5) "It would be interesting to change the loop count to see if you can
localize the "slowdown".  Or profile the code using a high resolution
timer or a hardware performance counter (e.g. PAPI or perfex) to see
where the additional time is spent."
By the loop counter, do you mean the outer or inner loop? Could you
be a little more specific on profiling the code using a high resolution
timer? Do I need a special profiler?

Many thanks,
Ge

.

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