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NAME
     dsttrf - compute the factorization of a symmetric  tridiago-
     nal matrix A

SYNOPSIS
     SUBROUTINE DSTTRF( N, L, D, SUBL, IPIV, INFO )

     INTEGER INFO, N

     DOUBLE PRECISION D( * )

     DOUBLE PRECISION L( * ), SUBL( * )



     #include <sunperf.h>

     void dsttrf(int n, double *l, double *d, double  *subl,  int
               *info) ;

PURPOSE
     DSTTRF computes the factorization  of  a  complex  Hermitian
     tridiagonal matrix A.


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

     L         (input/output) DOUBLE PRECISION  array,  dimension
               (N)
               On entry, the n-1 subdiagonal elements of the tri-
               diagonal  matrix A.  On exit, part of the factori-
               zation of A.

     D         (input/output) DOUBLE PRECISION  array,  dimension
               (N)
               On entry, the n diagonal elements of the tridiago-
               nal matrix A.  On exit, the n diagonal elements of
               the diagonal matrix D from the L*D*L**T factoriza-
               tion of A.

     SUBL      (output) DOUBLE PRECISION array, dimension (N)
               On exit, part of the factorization of A.

     IPIV      (output) INTEGER array, dimension (N)
               On exit, the pivot indices of the factorization.

     INFO      (output) INTEGER
               = 0:  successful exit
               < 0:  if INFO = -i, the i-th argument had an ille-
               gal value
               > 0:  if INFO = i, D(k,k) is  exactly  zero.   The
               factorization  has  been  completed, but the block
               diagonal matrix D is exactly singular and division
               by zero will occur if it is used to solve a system
               of equations.

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