DGBSV: incorrect numerical results with -L/usr/lib64/atlas ?

[Thomas Koenig]

Hi Jorge,

> I do not know if this forum is the most appropriate, but as it based
> using gfortran I will try to start here.
> 
> I usually build the ATLAS library in some beta version without any
> numerical problem that I remember. In a circumstantial way, I have to
> use the system ATLAS library and, today, I am getting some incorrect
> numerical results with the DGBSV lapack fortran subroutine, which is
> described below with a simple test.
> 
> Perhaps, I am not using the correct sintaxis in the interface, maybe
> in the compiler flags or the link ones? Please, any ideas?
> Thanks in advance.

I tried your code against the reference LAPACK and got the result below,
which also has info=1 at the end.  There is no argument mismatch
(at least) in the called routine, I checked that by including the
refblas routine into the source.

So, I don't know what's wrong.  Possibly something with the numerics,
or a wrong size of an argument?  It would be possible to compile the
reference LAPACK and BLAS with debugging and check with a debugger
where the info flag is set.

If I may guess, it's probably an error in one of the array sizes -
LAPACK is notorious that way.  I wish they would use modern Fortran's
array passing mechanism.

Best regards

	Thomas