From bug-octave-request at bevo dot che dot wisc dot edu  Tue Jun  5 09:29:39 2001
Subject: det() hangs on large matrix
From: ptdeboer at cs dot utwente dot nl (Pieter-Tjerk de Boer)
To: bug-octave at bevo dot che dot wisc dot edu
Cc: ptdeboer at cs dot utwente dot nl
Date: Tue, 5 Jun 2001 16:29:33 +0200 (MET DST)

Bug report for Octave 2.0.16 configured for sparc-sun-solaris2.6

Description:
-----------

For some large matrices, trying to calculate the determinant using det()
seems to hang Octave.  I.e., for as long as I have waited, no answer (nor an
error message and/or prompt) appears, while for other matrices of the same
size and similar content the answer appears within a second or so.


Repeat-By:
---------

- Download the following file (size is about 200 kB):
    http://www.cs.utwente.nl/~ptdeboer/det_hangs.dat.gz
- Gunzip it
- Start Octave, and load the file; this loads a matrix called 'mm1' of
  size 161 x 161
- Type  det(mm1)
  On my machine, after 20 minutes Octave is still busy with this example.

Note that I expect (given the problem in which this matrix came up) that if
the calculation wouldn't hang, Octave would warn that the matrix is singular
to machine precision and return a determinant of 0.

For comparison, typing  det (mm1(1:155,1:155))   produces an answer almost
immediately.


Fix:
---

I don't have one, unfortunately.


Configuration (please do not edit this section):
-----------------------------------------------

uname output:     SunOS erlang 5.6 Generic_105181-23 sun4u sparc SUNW,Ultra-5_10
configure opts:   --prefix=/home/kam/ptdeboer/octave-2.0.16
Fortran compiler: f77
FFLAGS:           -O
F2C:              
F2CFLAGS:         
FLIBS:            -R/opt/SUNWspro/lib  -L/opt/SUNWspro/lib -L/opt/SUNWspro/WS6/lib -L/usr/ccs/lib -L/usr/lib -lF77 -lM77 -lsunmath -lm -lcx
CPPFLAGS:         
INCFLAGS:         -I/home/kam/ptdeboer/octave-2.0.16/include -I/home/kam/ptdeboer/octave-2.0.16/include/octave-2.0.16
C compiler:       gcc, version 2.95.3 20010315 (release)
CFLAGS:           -DHAVE_CONFIG_H  -g -O2 -Wall
CPICFLAG:         -fPIC
C++ compiler:     c++, version 2.95.3 20010315 (release)
CXXFLAGS:         -DHAVE_CONFIG_H -fno-rtti -fno-exceptions -fno-implicit-templates -g -O2 -Wall
CXXPICFLAG:       -fPIC
LDFLAGS:          -g
LIBFLAGS:         -L/home/kam/ptdeboer/octave-2.0.16/lib/octave-2.0.16
RLD_FLAG:         -Xlinker -R -Xlinker /home/kam/ptdeboer/octave-2.0.16/lib/octave-2.0.16
TERMLIBS:         -lncurses
LIBS:             
LEXLIB:           
LIBPLPLOT:        
LIBDLFCN:         
DEFS:

  -DOCTAVE_SOURCE=1 -DSEPCHAR=':' -DSEPCHAR_STR=":" -DUSE_READLINE=1
  -D__NO_MATH_INLINES=1 -DCXX_NEW_FRIEND_TEMPLATE_DECL=1 -DHAVE_LIBM=1
  -DF77_APPEND_UNDERSCORE=1 -DHAVE_LIBSOCKET=1 -DSIZEOF_SHORT=2
  -DSIZEOF_INT=4 -DSIZEOF_LONG=4 -DHAVE_ALLOCA_H=1 -DHAVE_ALLOCA=1
  -DNPOS=string::npos -DSTDC_HEADERS=1 -DHAVE_DIRENT_H=1
  -DTIME_WITH_SYS_TIME=1 -DHAVE_SYS_WAIT_H=1 -DHAVE_ASSERT_H=1
  -DHAVE_CURSES_H=1 -DHAVE_DLFCN_H=1 -DHAVE_FCNTL_H=1 -DHAVE_FLOAT_H=1
  -DHAVE_FLOATINGPOINT_H=1 -DHAVE_FNMATCH_H=1 -DHAVE_GLOB_H=1
  -DHAVE_GRP_H=1 -DHAVE_IEEEFP_H=1 -DHAVE_LIMITS_H=1 -DHAVE_MEMORY_H=1
  -DHAVE_NAN_H=1 -DHAVE_POLL_H=1 -DHAVE_PWD_H=1 -DHAVE_SGTTY_H=1
  -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_SYS_IOCTL_H=1
  -DHAVE_SYS_PARAM_H=1 -DHAVE_SYS_POLL_H=1 -DHAVE_SYS_RESOURCE_H=1
  -DHAVE_SYS_SELECT_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_SYS_TIME_H=1
  -DHAVE_SYS_TIMES_H=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_UTSNAME_H=1
  -DHAVE_TERMIO_H=1 -DHAVE_TERMIOS_H=1 -DHAVE_UNISTD_H=1
  -DHAVE_VARARGS_H=1 -DHAVE_ATEXIT=1 -DHAVE_BCOPY=1 -DHAVE_BZERO=1
  -DHAVE_DUP2=1



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