Hi,
The simple program below performs a sum over diagonal entries in a 4-dimensional array of REAL numbers. The result should be 6.
When compiled via
ifort -r8 -O3 -o test test.f90
it gives get the correct result. However, when compiled to produce code with SSE3 via
ifort -r8 -O3 -xP -o test test.f90
the result is 1 instead of 6.
Same with ifort 9.1 and ifort 10.1, on Pentium 4 32 bit Scientific Linux 5.2 and Xeon 5160 64 bit ClusterVisionOS 2.1. Also with -xN instead of -xP on a Pentium M with OpenSUSE 10.3
Interestingly, when the order of the inner and outer loops is interchanged, the error does not appear anymore.
It would be great if someone could test this. Am I missing something?
Thanks, Stefan
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PROGRAM test
IMPLICIT NONE
REAL, DIMENSION(3, 2, 3, 2) :: a
a=0.0
a(1, 1, 1, 1)=1.0
a(2, 1, 2, 1)=1.0
a(3, 1, 3, 1)=1.0
a(1, 2, 1, 2)=1.0
a(2, 2, 2, 2)=1.0
a(3, 2, 3, 2)=1.0
PRINT *, f(a)
CONTAINS
FUNCTION f(a)
REAL :: f
REAL, DIMENSION(3, 2, 3, 2), INTENT(IN) :: a
INTEGER :: c, s
f=0.0
DO s=1, 2
DO c=1, 3
f=f+a(c, s, c, s)
END DO
END DO
END FUNCTION f
END PROGRAM test
