[Bug fortran/38955] New: testsuite/gfortran.dg/array_constructor_24.f fails due to floating point comparison

["billingd at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

With recent trunk (4.4.0 20090107), test gfortran.dg/array_constructor_24.f
fails on i686-pc-cygwin for the four -O3 execution tests.  The failure is in
subroutine FA6013.

      program try_fa6013
      call fa6013 (10, 1, -1)
      call fa6077 (10, 1, -1, (/1,2,3,4,5,6,7,8,9,10/))
      call fa2083
      end program

      subroutine  FA6013 (nf10, nf1, mf1)
      integer, parameter :: kv = 4
      REAL(KV) DDA1(10)
      REAL(KV) DDA2(10)
      REAL(KV) DDA(10), dval
      dda = (/1,2,3,4,5,6,7,8,9,10/)
      DDA1 = ATAN2 ((/(REAL(J1,KV),J1=1,10)/),
     $                 REAL((/(J1,J1=nf10,nf1,mf1)/), KV))   !fails
      DDA2 = ATAN2 (DDA, DDA(10:1:-1))
      if (any (abs(DDA1-DDA2) .gt. 1.0e-6)) call abort ()
      END

On investigation, I found that all the components of arrays DDA1 and DDA2 were
equal, but the test "(any (DDA1 .ne. DDA2))" fails.  It looks like a typical
ix86 excess precision problem when comparing floating point number for
equality.  

The following patch allows the test to pass.

--- array_constructor_24.f.orig 2009-01-24 13:14:35.828125000 +1100
+++ array_constructor_24.f      2009-01-24 12:43:50.203125000 +1100
@@ -19,7 +19,7 @@
       DDA1 = ATAN2 ((/(REAL(J1,KV),J1=1,10)/),
      $                 REAL((/(J1,J1=nf10,nf1,mf1)/), KV))   !fails
       DDA2 = ATAN2 (DDA, DDA(10:1:-1))
-      if (any (DDA1 .ne. DDA2)) call abort ()
+      if (any (abs(DDA1-DDA2) .gt. 1.0e-6)) call abort ()
       END

       subroutine FA6077 (nf10,nf1,mf1, ida)


-- 
           Summary: testsuite/gfortran.dg/array_constructor_24.f  fails due
                    to floating point comparison
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: billingd at gcc dot gnu dot org
 GCC build triplet: i686-pc-cygwin
  GCC host triplet: i686-pc-cygwin
GCC target triplet: i686-pc-cygwin


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38955