A positive value of INFO on return from an LAPACK routine indicates a failure in the course of the algorithm. Common causes are:

- a matrix is singular (to working precision);
- a symmetric matrix is not positive definite;
- an iterative algorithm for computing eigenvalues or eigenvectors fails to converge in the permitted number of iterations.

When a failure with INFO > 0 occurs, control is *always* returned
to the calling program; XERBLA is *not* called, and no error message
is written.
It is worth repeating that it is good practice always to check for
a non-zero value of INFO on return from an LAPACK routine.

A failure with INFO > 0 may indicate any of the following:

- an inappropriate routine was used:
for example, if a routine fails because a symmetric matrix turns out not to be
positive definite, consider using a routine for symmetric indefinite matrices.
- a single precision routine was used when double precision was needed:
for example, if SGESVX reports approximate singularity
(as illustrated above), the corresponding double precision routine DGESVX
may be able to solve the problem (but nevertheless the problem is
ill-conditioned).
- a programming error occurred in generating the data supplied
to a routine: for example, even though theoretically a matrix should be
well-conditioned and positive-definite, a programming error in generating
the matrix could easily destroy either of those properties.
- a programming error occurred in calling the routine, of the kind
listed in Section 7.1.

Tue Nov 29 14:03:33 EST 1994