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NAME
     dsyev - compute all eigenvalues and,  optionally,  eigenvec-
     tors of a real symmetric matrix A

SYNOPSIS
     SUBROUTINE DSYEV( JOBZ, UPLO, N, A,  LDA,  W,  WORK,  LWORK,
               INFO )

     CHARACTER JOBZ, UPLO

     INTEGER INFO, LDA, LWORK, N

     DOUBLE PRECISION A( LDA, * ), W( * ), WORK( * )



     #include <sunperf.h>

     void dsyev(char jobz, char uplo, int n, double *da, int lda,
               double *w, int *info) ;

PURPOSE
     DSYEV computes all eigenvalues and, optionally, eigenvectors
     of a real symmetric matrix A.


ARGUMENTS
     JOBZ      (input) CHARACTER*1
               = 'N':  Compute eigenvalues only;
               = 'V':  Compute eigenvalues and eigenvectors.

     UPLO      (input) CHARACTER*1
               = 'U':  Upper triangle of A is stored;
               = 'L':  Lower triangle of A is stored.

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

     A         (input/output) DOUBLE PRECISION  array,  dimension
               (LDA, N)
               On entry, the symmetric matrix A.  If UPLO =  'U',
               the leading N-by-N upper triangular part of A con-
               tains the upper triangular part of the  matrix  A.
               If UPLO = 'L', the leading N-by-N lower triangular
               part of A contains the lower  triangular  part  of
               the  matrix  A.   On  exit, if JOBZ = 'V', then if
               INFO = 0, A contains the orthonormal  eigenvectors
               of  the matrix A.  If JOBZ = 'N', then on exit the
               lower triangle (if UPLO='L') or the upper triangle
               (if  UPLO='U')  of  A,  including the diagonal, is
               destroyed.

     LDA       (input) INTEGER
               The leading dimension of  the  array  A.   LDA  >=
               max(1,N).

     W         (output) DOUBLE PRECISION array, dimension (N)
               If INFO = 0, the eigenvalues in ascending order.

     WORK      (workspace/output) DOUBLE PRECISION array,  dimen-
               sion (LWORK)
               On exit, if INFO = 0, WORK(1) returns the  optimal
               LWORK.

     LWORK     (input) INTEGER
               The  length  of  the   array   WORK.    LWORK   >=
               max(1,3*N-1).   For  optimal  efficiency, LWORK >=
               (NB+2)*N, where NB is  the  blocksize  for  DSYTRD
               returned by ILAENV.

     INFO      (output) INTEGER
               = 0:  successful exit
               < 0:  if INFO = -i, the i-th argument had an ille-
               gal value
               > 0:  if INFO = i, the algorithm  failed  to  con-
               verge;  i off-diagonal elements of an intermediate
               tridiagonal form did not converge to zero.

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