[Bug fortran/38188] Inconsistent function results depending on irrelevant write statement

[dojo at masterleep dot com]

--- Comment #3 from dojo at masterleep dot com  2008-11-20 17:55 ---
Oops, sorry for missing that.  Thank you for the help.  I was led astray
because for mysterious reasons it "always worked before"...


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dojo at masterleep dot com changed:

   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution||INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38188

[Bug fortran/38188] Inconsistent function results depending on irrelevant write statement

[burnus at gcc dot gnu dot org]

--- Comment #2 from burnus at gcc dot gnu dot org  2008-11-20 07:20 ---
> I don't think INF is the same as infinity. It is most like implict  
> declared variable with an undefined value.

Exactly. With IMPLICIT NONE one sees that INF is an (implicitly typed) integer
variable, which has an undefined value.

minval = +INF
maxval = -INF

How about:

minval = huge(minval) ! largest finite value
maxval = -huge(minval)! smallest finite value

or shorter (untested)

  min = minval(arr( [(1+kcycle*i, i=0,npts-1)] )
  max = maxval(arr( [(1+kcycle*i, i=0,npts-1)] )

where (g)Fortran does internally what you want.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38188

[Bug fortran/38188] Inconsistent function results depending on irrelevant write statement

[pinskia at gmail dot com]

--- Comment #1 from pinskia at gmail dot com  2008-11-20 07:05 ---
Subject: Re:   New: Inconsistent function results depending on irrelevant write
statement

I don't think INF is the same as infinity. It is most like implict  
declared variable with an undefined value.

Sent from my iPhone

On Nov 19, 2008, at 10:52 PM, "dojo at masterleep dot com"
<[EMAIL PROTECTED] 
 > wrote:

> I am getting unreliable results from a small function using the latest
> prepackaged Mac OS build (PPC) available from the wiki download  
> page.  The
> function behaves correctly if an otherwise irrelevant write  
> statement is added.
> When the statement is removed, the function returns gibberish.  This  
> is
> ancient code which worked on older versions of gfortran, so  
> hopefully I haven't
> overlooked an obvious problem...
>
> $ uname -a
> Darwin Numenor 9.5.0 Darwin Kernel Version 9.5.0: Wed Sep  3  
> 11:29:43 PDT 2008;
> root:xnu-1228.7.58~1/RELEASE_I386 i386
>
> $ gfortran --version
> GNU Fortran (GCC) 4.4.0 20080823 (experimental) [trunk revision  
> 139508]
>
> $ cat xx.f
>program xx
>real xa(102)
>do 10 i=1,100
> 10  xa(i)=float(i)
>call scale (xa,23.,100,1)
>write (*,*) xa(101), xa(102)
>end
>
>
>subroutine scale(arr,axlen,npts,kcycle)
>real :: arr(*),axlen,minval,maxval,val
>integer :: npts,kcycle
>minval = +INF
>maxval = -INF
>do i=0,npts-1
>val=arr(1+kcycle*i)
>minval=amin1(val,minval)
>maxval=amax1(val,maxval)
>end do
>arr(npts*kcycle+1)=minval
>arr(npts*kcycle+kcycle+1)=(maxval-minval)/axlen
> c   If the following line is uncommented, the function will work
> c   write (*,*) 3
>end subroutine scale
>
>
> # Correct function result (write statement is left in)
> $ gfortran -o xx xx.f
> $ xx
>   3
>   0.000   4.3478260
>
> # Incorrect function result (write statement is commented out)
> $ gfortran -o xx xx.f
> $ xx
> -2.13906214E+09  1.86005408E+08
>
>
> -- 
>   Summary: Inconsistent function results depending on  
> irrelevant
>write statement
>   Product: gcc
>   Version: unknown
>Status: UNCONFIRMED
>  Severity: major
>  Priority: P3
> Component: fortran
>AssignedTo: unassigned at gcc dot gnu dot org
>ReportedBy: dojo at masterleep dot com
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38188
>


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38188