Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!sobmips!laporte
From: laporte@sobmips.UUCP (p.laporte)
Newsgroups: comp.sys.mips
Subject: f77 bug
Message-ID: <1990Feb1.170639.15889@sobmips.UUCP>
Date: 1 Feb 90 17:06:39 GMT
Organization: Sobeco Group - Montreal, Canada
Lines: 124

We have found what we think is a bug in the fortran compiler (version 2.0)

Here is a small program that demonstrate the problem. When we use the 
optimiser we get incorrect results when doing a simple addition.

Maybee someone at mips could tell me if they were aware of this bug and
if there is a patch for it.

Tks

-----
      implicit double precision(a-h, o-z)
      
      common ia,r(12),tb
      data tb  / 0.02d0 /
      r(4) = 4.0
      r(5) = 1.0
      r(6) = 2.0
      r(7) = 3.0
      write (*,10) r(4),r(5),r(6),r(7)
      r1  = r(5)+r(6)
      r2  = r(5)+r(7)
      r3  = r(5)+r(6)+r(7)
      write(*,20) r1, r2,r3
      write(*,20) r(5)+r(6),r(5)+r(7),r(5)+r(6)+r(7)
10    format ( " R(4)=",F8.5 "   R(5)=",F8.5  "   R(6)=",F8.5  
     1    "   R(7)=",F8.5 //)
20    format ( " R(5)+R(6)=", F8.5/ " R(5)+R(7)=",F8.5/ 
     1    " R(5)+R(6)+R(7)=",F8.5 // )
      stop
      end      

--------------------------------------------------
          without any option
 R(4)= 4.00000   R(5)= 2.00000   R(6)= 0.00000   R(7)= 3.00000


 R(5)+R(6)= 4.00000
 R(5)+R(7)= 5.00000
 R(5)+R(6)+R(7)= 7.00000


 R(5)+R(6)= 4.00000
 R(5)+R(7)= 5.00000
 R(5)+R(6)+R(7)= 7.00000


--------------------------------------------------
          with -O0 option
 R(4)= 4.00000   R(5)= 1.00000   R(6)= 2.00000   R(7)= 3.00000


 R(5)+R(6)= 3.00000
 R(5)+R(7)= 4.00000
 R(5)+R(6)+R(7)= 6.00000


 R(5)+R(6)= 3.00000
 R(5)+R(7)= 4.00000
 R(5)+R(6)+R(7)= 6.00000


--------------------------------------------------
          with -O1 option
 R(4)= 4.00000   R(5)= 2.00000   R(6)= 0.00000   R(7)= 3.00000


 R(5)+R(6)= 4.00000
 R(5)+R(7)= 5.00000
 R(5)+R(6)+R(7)= 7.00000


 R(5)+R(6)= 4.00000
 R(5)+R(7)= 5.00000
 R(5)+R(6)+R(7)= 7.00000


--------------------------------------------------
          with -O2 option
 R(4)= 4.00000   R(5)= 2.00000   R(6)= 0.00000   R(7)= 3.00000


 R(5)+R(6)= 4.00000
 R(5)+R(7)= 5.00000
 R(5)+R(6)+R(7)= 7.00000


 R(5)+R(6)= 4.00000
 R(5)+R(7)= 5.00000
 R(5)+R(6)+R(7)= 7.00000


--------------------------------------------------
          with -O3 option
 R(4)= 4.00000   R(5)= 2.00000   R(6)= 0.00000   R(7)= 3.00000


 R(5)+R(6)= 4.00000
 R(5)+R(7)= 5.00000
 R(5)+R(6)+R(7)= 7.00000


 R(5)+R(6)= 4.00000
 R(5)+R(7)= 5.00000
 R(5)+R(6)+R(7)= 7.00000


--------------------------------------------------
          with -O0 and -g options
 R(4)= 4.00000   R(5)= 1.00000   R(6)= 2.00000   R(7)= 3.00000


 R(5)+R(6)= 3.00000
 R(5)+R(7)= 4.00000
 R(5)+R(6)+R(7)= 6.00000


 R(5)+R(6)= 3.00000
 R(5)+R(7)= 4.00000
 R(5)+R(6)+R(7)= 6.00000


Pierre Laporte
{attcan,mcgill-vision,telly}!sobeco!laporte