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LAPACK version 3.0
ssyev(3)

PURPOSE
  SSYEV - compute all eigenvalues and, optionally, eigenvectors of a real
  symmetric matrix A

SYNTAX
  SUBROUTINE SSYEV( JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, INFO )

      CHARACTER	    JOBZ, UPLO

      INTEGER	    INFO, LDA, LWORK, N

      REAL	    A( LDA, * ), W( * ), WORK( * )

DESCRIPTION
  SSYEV 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) REAL array, dimension (LDA, N)
	  On entry, the symmetric matrix A.  If UPLO = 'U', the leading N-
	  by-N upper triangular part of A contains 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) REAL array, dimension (N)
	  If INFO = 0, the eigenvalues in ascending order.

  WORK	  (workspace/output) REAL array, dimension (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 SSYTRD
	  returned by ILAENV.

	  If LWORK = -1, then a workspace query is assumed; the routine only
	  calculates the optimal size of the WORK array, returns this value
	  as the first entry of the WORK array, and no error message related
	  to LWORK is issued by XERBLA.

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