** On entry to SGESV parameter number 4 had an illegal valueThis particular message would be caused by passing to SGESV a value of LDA which was less than the value of the argument N. The documentation for SGESV in Part 2 states the set of acceptable input values: ``LDA
In the model implementation of XERBLA which is supplied with LAPACK, execution stops after the message; but the call to XERBLA is followed by a RETURN statement in the LAPACK routine, so that if the installer removes the STOP statement in XERBLA, the result will be an immediate exit from the LAPACK routine with a negative value of INFO. It is good practice always to check for a non-zero value of INFO on return from an LAPACK routine. (We recommend however that XERBLA should not be modified to return control to the calling routine, unless absolutely necessary, since this would remove one of the built-in safety-features of LAPACK.)