Re: [Bug-gsl] Re: infinite loop in gsl_eigen_symm

[Andries E. Brouwer]

On Mon, Aug 27, 2007 at 10:21:04PM +0100, Brian Gough wrote:
> At Wed, 22 Aug 2007 17:30:18 +0200,
> Andries E. Brouwer wrote:
>>> In a program that has called gsl_eigen_symm() successfully 10^9 times,
>>> I find that on one specific matrix this routine hangs in an infinite loop.
>>> Trying this same matrix on a different architecture, all is well.
>>> 
>>> The machine with infinite loop is an x86_64:
>>> Intel(R) Core(TM)2 CPU 6300 @ 1.86GHz
> 
> Thanks for the bug report.  Can you send me a complete list of the
> compiler version, operating system version and options used to compile
> GSL so I can try to reproduce the problem.

% cc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v 
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr 
--enable-shared --with-system-zlib --libexecdir=/usr/lib 
--without-included-gettext --enable-threads=posix --enable-nls 
--program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu 
--enable-libstdcxx-debug --enable-mpfr --enable-checking=release 
x86_64-linux-gnu
Thread model: posix
gcc version 4.1.2 (Ubuntu 4.1.2-0ubuntu4)

% cat /proc/version
Linux version 2.6.20-13-generic (address@hidden) (gcc version 4.1.2 (Ubuntu 
4.1.2-0ubuntu4)) #2 SMP Sat Mar 24 23:12:02 UTC 2007

No special options were used to compile gsl, I think just
 ./configure; make; make install
The bug was encountered with gsl 1.7. I tried 1.9 instead,
but the bug was still there.

Fragments of config.h:

#define HAVE_DECL_ACOSH 1
#define HAVE_DECL_ASINH 1
#define HAVE_DECL_ATANH 1
#define HAVE_DECL_EXPM1 1
#define HAVE_DECL_FEENABLEEXCEPT 1
#define HAVE_DECL_FESETTRAPENABLE 0
#define HAVE_DECL_FINITE 1
#define HAVE_DECL_FREXP 1
#define HAVE_DECL_HYPOT 1
#define HAVE_DECL_ISFINITE 0
#define HAVE_DECL_ISINF 1
#define HAVE_DECL_ISNAN 1
#define HAVE_DECL_LDEXP 1
#define HAVE_DECL_LOG1P 1
#define HAVE_DLFCN_H 1
#define HAVE_INTTYPES_H 1
#define HAVE_LIBM 1
#define HAVE_PRINTF_LONGDOUBLE 1
#define HAVE_GNUX86_IEEE_INTERFACE 1
#define HAVE_IEEE_COMPARISONS 1
#define HAVE_IEEE_DENORMALS 1

> I expect it is caused by different underflow behaviour with some
> recent 64bit or SSE instructions -- I haven't been able to reproduce
> it compiling with -msse2 -fpmath=sse on a 32-bit machine.

% cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Core(TM)2 CPU          6300  @ 1.86GHz
stepping        : 2
cpu MHz         : 1862.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm 
constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
bogomips        : 3739.68
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor       : 1
... same stuff once more ...

Andries