Article ID: 74220
Article Last Modified on 12/1/2003
APPLIES TO
- Microsoft FORTRAN Compiler 4.0
- Microsoft FORTRAN Compiler 4.01
- Microsoft FORTRAN Compiler 4.1
- Microsoft FORTRAN Compiler 5.0
- Microsoft FORTRAN Compiler 4.1
- Microsoft FORTRAN Compiler 5.0
This article was previously published under Q74220
SYMPTOMS
Compiling code using Microsoft FORTRAN versions 4.0, 4.01, 4.1, and 5.0 under MS-DOS, and versions 4.1 and 5.0 under OS/2, when that code contains a subroutine with nested DO-loops in which arrays are indexed using a DO variable from an outer DO-loop, may generate the following error:
RESOLUTION
The error can be suppressed by turning off loop optimization, using a temporary variable in place of the DO variable from the outer DO-loop, or by upgrading to FORTRAN 5.1.
STATUS
Microsoft has confirmed this to be a problem in Microsoft FORTRAN versions 4.0, 4.01, 4.1, and 5.0 for MS-DOS and versions 4.1 and 5.0 for OS/2. This problem was corrected in Microsoft FORTRAN 5.1.
MORE INFORMATION
This error is caused by a problem with loop optimization. The following code generates the F1001 error:
Sample code
subroutine test(a,b,n)
real*8 a(6,12), b(6,6)
do 20 i=1,n
do 10 j=1,n
a(i,j+n)=b(i,j)
10 continue
20 continue
return
end
Compiling with the /Od option or with the /Odct options suppresses the error. Microsoft FORTRAN version 5.1 will not generate the error.
If a temporary variable is used in place of the DO variable "i" in the array subscript, the error will not generated. This allows full optimization to be used when compiling. The following code demonstrates this solution:
subroutine test(a,b,n)
real*8 a(6,12), b(6,6)
do 20 i=1,n
ii = i ! Temporary variable assigned value of i
do 10 j=1,n
a(ii,j+n)=b(ii,j) ! Temporary variable used in place of i
10 continue
20 continue
return
end
Additional query words: 4.00 4.01 4.10 5.00
Keywords: kbfix KB74220
