DSTERF(3)      LAPACK routine of NEC Numeric Library Collection      DSTERF(3)



NAME
       DSTERF

SYNOPSIS
       SUBROUTINE DSTERF (N, D, E, INFO)



PURPOSE
            DSTERF computes all eigenvalues of a symmetric tridiagonal matrix
            using the Pal-Walker-Kahan variant of the QL or QR algorithm.




ARGUMENTS
           N         (input)
                     N is INTEGER
                     The order of the matrix.  N >= 0.

           D         (input/output)
                     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         (input/output)
                     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      (output)
                     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.



LAPACK routine                  31 October 2017                      DSTERF(3)