## On entry to DGEEVX parameter number 4 had an illegal value

Open discussion regarding features, bugs, issues, vendors, etc.

### On entry to DGEEVX parameter number 4 had an illegal value

I got this message, what's the problem in my program?? How can I solve it ??

Thank you very much!
GNOW MAS

Posts: 10
Joined: Sun Apr 24, 2011 11:31 am

### Re: On entry to DGEEVX parameter number 4 had an illegal va

My program is written in f95 code, does it create trouble??
GNOW MAS

Posts: 10
Joined: Sun Apr 24, 2011 11:31 am

### Re: On entry to DGEEVX parameter number 4 had an illegal va

Could you give your calling sequence?
It seems that the 4th parameter: SENSE is wrong.

From the routine:

* SENSE (input) CHARACTER*1
* Determines which reciprocal condition numbers are computed.
* = 'N': None are computed;
* = 'E': Computed for eigenvalues only;
* = 'V': Computed for right eigenvectors only;
* = 'B': Computed for eigenvalues and right eigenvectors.
*
* If SENSE = 'E' or 'B', both left and right eigenvectors
* must also be computed (JOBVL = 'V' and JOBVR = 'V').

Checke especially the last condition if SENSE 'E' or 'B'. Are JOBVL and JOBVR set to 'V'?

Julie

Posts: 614
Joined: Wed Dec 08, 2004 7:07 pm

### Re: On entry to DGEEVX parameter number 4 had an illegal va

This is my calling sequence

CALL DGEEVX( 'N', 'N', 'N', 'E', n, A, n, Er, Ei, &
UL, LDVL, UR, LDVR, ILO, IHI, SCALE, ABNRM, &
RCONDE, RCONDV, WORK, LWORK, IWORK, INFO )

I am going to compute the eigenvalues, so it should be 'E', right ???
GNOW MAS

Posts: 10
Joined: Sun Apr 24, 2011 11:31 am

### Re: On entry to DGEEVX parameter number 4 had an illegal va

* If SENSE = 'E' or 'B', both left and right eigenvectors
* must also be computed (JOBVL = 'V' and JOBVR = 'V').

So you want
Code: Select all
`CALL DGEEVX( 'N', 'V', 'V', 'E', ... ) `

Posts: 614
Joined: Wed Dec 08, 2004 7:07 pm

### Re: On entry to DGEEVX parameter number 4 had an illegal va

oh, I see, I missed this information, thank you very much
Let me try it again
GNOW MAS

Posts: 10
Joined: Sun Apr 24, 2011 11:31 am

### Re: On entry to DGEEVX parameter number 4 had an illegal va

By the way, I am going to solve the eigenvalues of a second order differential equation

thus I solve the eigenvalues of the finite differencing matrix

the matrix is tridiagonal, but not symmetric

I have searched through the list of routines of LAPACK

I cannot find routines for solving non-symmetric tridiagonal matrix

I want to know if there are any solvers that can solve the eigenvalues of a non-symmetric tridiagonal matrix

Thank you very much
GNOW MAS

Posts: 10
Joined: Sun Apr 24, 2011 11:31 am