Print

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Hello,

In my view these are both the same.  Any optimizer you paid money for
will recognize the variables to be unused outisde the subroutine and
will recignize references to ubound() to be a constant which may be
hoisted out of the inner loop.

If you've detected a speed difference, you may have uncovered
a compiler bug of some sort or other.

IMHO, of course.

"Nofal, Mostafa" wrote:
> 
> Dear Colleagues
> 
> I would like to get your opinion about the difference in speed between the
> following two options and why do you prefer one over the other.
> 
> Option 1
> --------
> Subroutine dosomething( a, b, c )
> IMPLICIT NONE
> REAL, INTENT(in) :: a(:,:)
> REAL, INTENT(in out) :: b(:,:), c(:)
> INTEGER :: i, j
>   DO i = 1, UBOUND(a,1)
>     DO j = 1,UBOUND(a,2)
>       ....
>     END DO
>   END DO
> RETURN
> END SUBROUTINE
> 
> Option 2
> --------
> Subroutine dosomething( a, b, c )
> IMPLICIT NONE
> REAL, INTENT(in) :: a(:,:)
> REAL, INTENT(in out) :: b(:,:), c(:)
> INTEGER :: i, j, length, width
>   length = UBOUND(a,1)
>   width = UBOUND(a,2)
>   DO i = 1, length
>     DO j = 1, width
>       ....
>     END DO
>   END DO
> RETURN
> END SUBROUTINE
> 
> Regards
> 
> 
> Mostafa Nofal, Ph.D.                    E-mail: [log in to unmask]
> Associate Research Officer              URL: http://www.nrc.ca/irc/bes/
> Building Envelope & Structure           tel. (613) 993-9672
> Institute for Research in Construction  fax (613) 954-3733
> National Research Council of Canada
> Bldg. M-24, Rm. 322A,
> 1500 Montreal Road, Ottawa, Ontario,
> Canada,         K1A 0R6
> 
>   ------------------------------------------------------------------------
> 
>    Part 1.2    Type: application/ms-tnef
>            Encoding: base64

-- 

Cheers!
Dan Nagle		[log in to unmask]
Purple Sage Computing Solutions, Inc.


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