Fortran - Auto-Parallization Question

Author

Auto-Parallization Question

Henry

2005-04-01, 8:57 am

Dear all,

I am working with auto-parallization in fortran
when I am dealing with following kind of looping,

do k=1,n
do j=1,n
do i=1,n <---- line 38
a(i,j,k) = b(i,j,k)+c(i,j,k)
enddo
enddo
enddo

An error message occured,
parallel loop: line 38 (failed partitioning)

But, it stated that the routine is successfully auto-parallelized.
Will the error affect the final solution?
I have tried that different solutions were obtained between
parellelized and non-parallelized one...

Please Help~~~~~~~~
THANK YOU

Henry

Richard Edgar

2005-04-01, 8:57 am

Henry wrote:
> I am working with auto-parallization in fortran
> when I am dealing with following kind of looping,
>
> do k=1,n
> do j=1,n
> do i=1,n <---- line 38
> a(i,j,k) = b(i,j,k)+c(i,j,k)
> enddo
> enddo
> enddo
>
> An error message occured,
> parallel loop: line 38 (failed partitioning)
>
> But, it stated that the routine is successfully auto-parallelized.
> Will the error affect the final solution?
> I have tried that different solutions were obtained between
> parellelized and non-parallelized one...

Compiler? Platform?

In general, you shouldn't expect the serial and parallel versions to
give exactly the same answers (if you don't know why.... learn a bit
more about floating point numbers), but if you have that exact test case
failing, I suspect you have a compiler bug. Without more information,
it's impossible to say.

Richard

Richard Maine

2005-04-01, 3:59 pm

laputa_y@yahoo.com (Henry) writes:

> I am working with auto-parallization in fortran
....
> An error message occured,
> parallel loop: line 38 (failed partitioning)
>
> But, it stated that the routine is successfully auto-parallelized.
> Will the error affect the final solution?

Auto-parallization is a feature of particular compilers - not of the
language in general. You are going to have to give people a hint
of what compiler you are talking about to have good odds of getting
much help. I won't know anyway - I've no experience with
auto-parallelization - but others might.

(Oh. And to forestall a common "problem" - "f77" or "f90" is
not sufficient to tell people what compiler you are talking about;
I'd suggest including a vendor name, compiler version, and
platform).

--
Richard Maine
email: my last name at domain
domain: summertriangle dot net

Henry

2005-04-01, 3:59 pm

Richard Edgar <rge21@astro.su.se> wrote in message news:<d2jbj2$bro$1@news.su.se>...
> Henry wrote:
>
> Compiler? Platform?
>
> In general, you shouldn't expect the serial and parallel versions to
> give exactly the same answers (if you don't know why.... learn a bit
> more about floating point numbers), but if you have that exact test case
> failing, I suspect you have a compiler bug. Without more information,
> it's impossible to say.
>
> Richard

Thanks Richard

I am using Intel fortran complier v.8 with VS.NET 2003 at Windows XP.
And, all the variables I am using are in real*8, will this affecting
the final solution?

Henry

Aart Bik

2005-04-01, 3:59 pm

"Henry" <laputa_y@yahoo.com> wrote in message
news:f6562db4.0503312356.5abf744c@posting.google.com...
> An error message occured,
> parallel loop: line 38 (failed partitioning)

Dear Henry,

This message is not an error message, but a compiler diagnostic that is only
generated when, using Windows syntax, switch -Qparallel (to enable automatic
parallelization) is combined with the switch -Qpar_report<n> (to control the
amount of diagnostics). Value n=1 reports successful parallelization only.
Value n=2 reports some diagnostics on why loops fail to parallelize as well
(although this may sound alarming, effectively this means that
auto-parallelization has not touched the loop).

Example (n=1 reports success only):

[C:/cmplr/temp] ifort -Qpar_report1 -Qparallel joho.f

....

joho.f(5) : (col. 8) remark: LOOP WAS AUTO-PARALLELIZED.

Note that you can post all Intel compiler specific questions on one of our
IDS forums at http://softwareforums.intel.com/ids.
--
Aart Bik
(working for, but not necessarily speaking for Intel)
http://www.aartbik.com/

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