[Bug fortran/18218] New: Miscompare in sixtrack benchmark caused by loss of precision

[Bug fortran/18218] New: Miscompare in sixtrack benchmark caused by loss of precision

[lei at il dot ibm dot com]

I could reproduce this problem only on power4 hardware,
running SUSE linux.

% uname -a
Linux regsuse01 2.6.5-7-pseries64 #1 SMP Thu Apr 8 15:55:41 UTC 2004 ppc64 ppc64
ppc64 GNU/Linux

% ~/gcc/bin/gfortran --version
GNU Fortran 95 (GCC 4.0.0 20041027 (experimental))

Running SIXTRACK spec benchmark results in a miscompare,
even with all optimizations turned off.  The miscompare is caused
by the following place in file eig66.f

      do 40 i=1,ndim2
        if(abs(reval(i)**2+aieval(i)**2 -one).gt.c1m10) then
          write(6,*) ' EIG6: EIGENVALUES OFF THE UNIT CIRCLE!'
          return
        endif

This code checks that the distance from computed complex
eigenvalues to the unit circle is no more than 10**-10.
With g77, the distance is about 10**-14, and I get similar
results on other platforms with gfortran.  On power4+gfortran
the distance is about 10**-8, which triggers the error
message and causes miscompare.

There is some possibility that this problem is related
to 17927.

-- 
           Summary: Miscompare in sixtrack benchmark caused by loss of
                    precision
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: lei at il dot ibm dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: powerpc64-unknown-linux-gnu
  GCC host triplet: powerpc64-unknown-linux-gnu
GCC target triplet: powerpc64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[jgrimm2 at us dot ibm dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jgrimm2 at us dot ibm dot
                   |                            |com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[lei at il dot ibm dot com]

------- Additional Comments From lei at il dot ibm dot com  2004-11-08 14:52 -------
(In reply to comment #0)
> I could reproduce this problem only on power4 hardware,
> running SUSE linux.

Reproduced on powerpc-apple-darwin, with mainline snapshot 2004-10-31.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
  GCC build triplet|powerpc64-unknown-linux-gnu |
   GCC host triplet|powerpc64-unknown-linux-gnu |
 GCC target triplet|powerpc64-unknown-linux-gnu |powerpc*-*-*
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2004-11-08 14:54:16
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[pbrook at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2004-11-08 14:54:16         |2004-11-09 22:09:51
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[pbrook at gcc dot gnu dot org]

------- Additional Comments From pbrook at gcc dot gnu dot org  2004-11-09 22:11 -------
I suspect this is an IO library bug. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |pbrook at gcc dot gnu dot
                   |dot org                     |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-11-10 02:16 -------
Subject: Bug 18218

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	pbrook@gcc.gnu.org	2004-11-10 02:16:08

Modified files:
	gcc/testsuite  : ChangeLog 
	libgfortran    : ChangeLog 
Added files:
	gcc/testsuite/gfortran.dg: read_float_1.f90 

Log message:
	PR fortran/18218
	* configure.ac: Check for strtof.
	* configure: Regenerate.
	* config.h.in: Regenerate.
	* io/read.c (convert_real): Use strtof if available.
	(convert_precision_real): Remove.
	(read_f): Avoid poor exponentiation algorithm.
	gcc/testsuite/
	* gfortran.dg/list_read.c: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.4567&r2=1.4568
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gfortran.dg/read_float_1.f90.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/ChangeLog.diff?cvsroot=gcc&r1=1.108&r2=1.109



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-11-10 02:19 -------
Subject: Bug 18218

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	pbrook@gcc.gnu.org	2004-11-10 02:19:27

Modified files:
	libgfortran    : config.h.in configure configure.ac 
	libgfortran/io : read.c 

Log message:
	PR fortran/18218
	* configure.ac: Check for strtof.
	* configure: Regenerate.
	* config.h.in: Regenerate.
	* io/read.c (convert_real): Use strtof if available.
	(convert_precision_real): Remove.
	(read_f): Avoid poor exponentiation algorithm.
	gcc/testsuite/
	* gfortran.dg/list_read.c: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/config.h.in.diff?cvsroot=gcc&r1=1.10&r2=1.11
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/configure.diff?cvsroot=gcc&r1=1.18&r2=1.19
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/configure.ac.diff?cvsroot=gcc&r1=1.13&r2=1.14
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/io/read.c.diff?cvsroot=gcc&r1=1.3&r2=1.4



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[pbrook at gcc dot gnu dot org]

------- Additional Comments From pbrook at gcc dot gnu dot org  2004-11-11 14:34 -------
Fixed. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218

[Bug fortran/18218] Miscompare in sixtrack benchmark caused by loss of precision

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218