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Re: RFA: Revamp fortran array types

On 08/19/2009 07:59 PM, Toon Moene wrote:
Steve Kargl wrote:

On Wed, Aug 19, 2009 at 06:43:13PM +0200, Toon Moene wrote:


The following code is perfectly OK:

DIMENSION A(10)
A = 10.0
CALL SUB(A,A)
END
SUBROUTINE SUB(A,B)
REAL, INTENT(IN) :: A(:), B(:)

What happens if you replace the last line with

REAL, INTENT(IN) :: A(:)
REAL, INTENT(OUT) :: B(:)


Fascinating. I *think* that - as long as you do not actually write to B
- you're in the clear.

I think even B(2) = A(1) would be fine. Or even

B(2:N:2) = A(1:N-1:2)

Long term, if the vectorizer supported this kind of masking it may get it into trouble because of aliasing.

Paolo

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