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[Lapack] Lapack's DGETRF+DGETRI for matrix inversion fails quite badly

Dear Lapack developers team,

I have been using lapack's DGETRF+DGETRI to do matrix inversion in a linux
box
running Fedora 7. Lapack and Blas libraries are from rpm packages
blas-3.1.1-1.fc7.i386.rpm
and lapack-3.1.1-1.fc7.i386.rpm.

DGETRF+DGETRI seem to work just fine but since my (fortran-77) program use
them for a
lot of matrixes I made a small program to test these two subroutines, by
generating random
4x4 matrixes to calculate their inverses. Everything went fine until I
decided to test the reaction
of  DGETRF+DGETRI when it finds two equal rows or two equal columns in the
matrix to be
inverted. To my surprise the routines sometimes still try to do the
inversion process. Eventually
I get a error flag from DGETRF+DGETRI when the matrix have two equal lines
but not always and
I never get an error message when the matrix has two equal columns. I guess,
this has something
to do about the LU decomposition behind the strategy of DGETRF+DGETRI to do
the matrix inversion.

Some examples of the matrixes where this has happened are shown below.

Of course, one should never call DGETRF+DGETRI to do matrix inversion when
the matrix has two
or more equal lines (or columns). Should I test the matrix myself before
calling DGETRF+DGETRI
or should these routines find out this kind of situation by themselves?

Thanks in advance for you attention,

Alex A. Schmidt
Dep. of Mathematics/UFSM, Brazil

                         4x4 matrix
                                                    4x4 inverse
                                               4x4 product

-1.6130E+00 -1.1020E+00 -1.6130E+00  2.2540E+00   -1.7889E+13  6.9052E+15
6.3183E+15  1.3882E+16    7.1933E-01 -5.5129E-02 -1.3698E+00  1.1371E+00
 2.4020E+00 -1.8960E+00  2.4020E+00  1.5350E+00    5.9788E-02 -3.6745E-02
-4.5782E-02  2.7993E-01    4.1761E-01 -5.2895E-01  1.7921E-02  2.9202E-01
-3.0010E+00 -4.2300E+00 -3.0010E+00 -7.7700E-01    1.7889E+13 -6.9052E+15
-6.3183E+15 -1.3882E+16   -5.2300E-01  4.3789E-01 -3.2938E-01  1.9254E-01
 1.6900E-01  2.8670E+00  1.6900E-01 -4.0700E-01    3.4841E-01 -1.1111E-01
-2.9752E-01 -3.7852E-01    2.9773E-02  1.2005E-01 -5.9453E-02  1.0029E+00


 3.3920E+00 -7.2800E-01 -1.4400E+00  3.3920E+00    1.5132E+16 -6.8311E+15
4.0857E+14 -1.4379E+16   -1.8125E+00 -2.2559E+00 -1.4188E+00  2.7344E-02
 1.4470E+00 -3.6190E+00 -3.7510E+00  1.4470E+00   -5.9252E-01  1.5156E-01
1.6178E-01  9.3682E-01    2.9590E+00 -2.1631E+00 -5.6195E-01 -5.6016E+00
-4.8280E+00  1.1900E+00 -2.8370E+00 -4.8280E+00    2.7498E-01 -2.5928E-01
-1.8376E-01 -5.2632E-01   -3.6172E+00  4.4102E+00  3.2223E+00 -3.0625E+00
 2.7450E+00  9.8700E-01  1.8600E-01  2.7450E+00   -1.5132E+16  6.8311E+15
-4.0857E+14  1.4379E+16   -2.4023E+00 -4.2715E+00 -1.2907E+00 -3.3359E+00


 4.2280E+00  3.4440E+00 -3.9640E+00  3.4440E+00    7.8510E-01 -9.7194E-01
-1.1424E+00 -9.5392E-01    6.1641E+00 -2.2148E+00 -5.5859E+00 -5.7617E+00
 1.7530E+00  3.4530E+00  4.2120E+00  3.4530E+00   -1.5059E+16  2.0766E+16
2.5755E+16  1.7998E+16    4.6445E+00 -3.3047E+00 -6.9297E+00  8.7891E-01
 3.7260E+00 -1.7950E+00 -2.6670E+00 -1.7950E+00   -1.2906E-01  1.6487E-01
7.2103E-02  3.1464E-03    4.9102E+00 -3.3594E-01 -6.8086E+00 -5.1992E+00
-3.8170E+00  1.4660E+00 -4.3600E+00  1.4660E+00    1.5059E+16 -2.0766E+16
-2.5755E+16 -1.7998E+16   -3.6875E+00  4.1543E+00  3.6836E+00  3.3594E+00
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