dsterf(3S)

NAME
     DSTERF - compute all eigenvalues of a symmetric tridiagonal matrix using
     the Pal-Walker-Kahan variant of the QL or QR algorithm

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

         INTEGER        INFO, N

         DOUBLE         PRECISION D( * ), E( * )

IMPLEMENTATION
     These routines are part of the SCSL Scientific Library and can be loaded
     using either the -lscs or the -lscs_mp option.  The -lscs_mp option
     directs the linker to use the multi-processor version of the library.

     When linking to SCSL with -lscs or -lscs_mp, the default integer size is
     4 bytes (32 bits). Another version of SCSL is available in which integers
     are 8 bytes (64 bits).  This version allows the user access to larger
     memory sizes and helps when porting legacy Cray codes.  It can be loaded
     by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
     only one of the two versions; 4-byte integer and 8-byte integer library
     calls cannot be mixed.

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) INTEGER
             The order of the matrix.  N >= 0.

     D       (input/output) 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) 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) 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.

SEE ALSO
     INTRO_LAPACK(3S), INTRO_SCSL(3S)
     This man page is available only online.