DSTERF computes all eigenvalues of a symmetric tridiagonal matrix


 using the Pal-Walker-Kahan variant of the QL or QR algorithm.

N

          N is INTEGER


          The order of the matrix.  N >= 0.

D

          D is DOUBLE PRECISION array, dimension (N)


          On entry, the n diagonal elements of the tridiagonal matrix.


          On exit, if INFO = 0, the eigenvalues in ascending order.

E

          E is DOUBLE PRECISION array, dimension (N-1)


          On entry, the (n-1) subdiagonal elements of the tridiagonal


          matrix.


          On exit, E has been destroyed.

INFO

          INFO is INTEGER


          = 0:  successful exit


          < 0:  if INFO = -i, the i-th argument had an illegal value


          > 0:  the algorithm failed to find all of the eigenvalues in


                a total of 30*N iterations; if INFO = i, then i


                elements of E have not converged to zero.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

December 2016