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Error Handling and the Diagnostic Argument INFO

All documented routines have a diagnostic argument INFO that indicates the success or failure of the computation, as follows:

- INFO = 0: successful termination

- INFO < 0: illegal value of one or more arguments -- no computation performed

- INFO > 0: failure in the course of computation

All driver and auxiliary routines check that input arguments such as N or LDA or option arguments of type character have permitted values. If an illegal value of the ith argument is detected, the routine sets INFO = -i, and then calls an error-handling routine XERBLA.

The standard version of XERBLA issues an error message and halts execution, so that no LAPACK routine would ever return to the calling program with INFO < 0. However, this might occur if a non-standard version of XERBLA is used.