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CentOS 7.0 - man page for ssyevd (centos section 3)

ssyevd.f(3)				      LAPACK				      ssyevd.f(3)

NAME
       ssyevd.f -

SYNOPSIS
   Functions/Subroutines
       subroutine ssyevd (JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, IWORK, LIWORK, INFO)
	    SSYEVD computes the eigenvalues and, optionally, the left and/or right eigenvectors
	   for SY matrices

Function/Subroutine Documentation
   subroutine ssyevd (characterJOBZ, characterUPLO, integerN, real, dimension( lda, * )A,
       integerLDA, real, dimension( * )W, real, dimension( * )WORK, integerLWORK, integer,
       dimension( * )IWORK, integerLIWORK, integerINFO)
	SSYEVD computes the eigenvalues and, optionally, the left and/or right eigenvectors for
       SY matrices

       Purpose:

	    SSYEVD computes all eigenvalues and, optionally, eigenvectors of a
	    real symmetric matrix A. If eigenvectors are desired, it uses a
	    divide and conquer algorithm.

	    The divide and conquer algorithm makes very mild assumptions about
	    floating point arithmetic. It will work on machines with a guard
	    digit in add/subtract, or on those binary machines without guard
	    digits which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or
	    Cray-2. It could conceivably fail on hexadecimal or decimal machines
	    without guard digits, but we know of none.

	    Because of large use of BLAS of level 3, SSYEVD needs N**2 more
	    workspace than SSYEVX.

       Parameters:
	   JOBZ

		     JOBZ is CHARACTER*1
		     = 'N':  Compute eigenvalues only;
		     = 'V':  Compute eigenvalues and eigenvectors.

	   UPLO

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

	   N

		     N is INTEGER
		     The order of the matrix A.  N >= 0.

	   A

		     A is 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

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

	   W

		     W is REAL array, dimension (N)
		     If INFO = 0, the eigenvalues in ascending order.

	   WORK

		     WORK is REAL array,
						    dimension (LWORK)
		     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

	   LWORK

		     LWORK is INTEGER
		     The dimension of the array WORK.
		     If N <= 1, 	      LWORK must be at least 1.
		     If JOBZ = 'N' and N > 1, LWORK must be at least 2*N+1.
		     If JOBZ = 'V' and N > 1, LWORK must be at least
							   1 + 6*N + 2*N**2.

		     If LWORK = -1, then a workspace query is assumed; the routine
		     only calculates the optimal sizes of the WORK and IWORK
		     arrays, returns these values as the first entries of the WORK
		     and IWORK arrays, and no error message related to LWORK or
		     LIWORK is issued by XERBLA.

	   IWORK

		     IWORK is INTEGER array, dimension (MAX(1,LIWORK))
		     On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.

	   LIWORK

		     LIWORK is INTEGER
		     The dimension of the array IWORK.
		     If N <= 1, 	       LIWORK must be at least 1.
		     If JOBZ  = 'N' and N > 1, LIWORK must be at least 1.
		     If JOBZ  = 'V' and N > 1, LIWORK must be at least 3 + 5*N.

		     If LIWORK = -1, then a workspace query is assumed; the
		     routine only calculates the optimal sizes of the WORK and
		     IWORK arrays, returns these values as the first entries of
		     the WORK and IWORK arrays, and no error message related to
		     LWORK or LIWORK is issued by XERBLA.

	   INFO

		     INFO is INTEGER
		     = 0:  successful exit
		     < 0:  if INFO = -i, the i-th argument had an illegal value
		     > 0:  if INFO = i and JOBZ = 'N', then the algorithm failed
			   to converge; i off-diagonal elements of an intermediate
			   tridiagonal form did not converge to zero;
			   if INFO = i and JOBZ = 'V', then the algorithm failed
			   to compute an eigenvalue while working on the submatrix
			   lying in rows and columns INFO/(N+1) through
			   mod(INFO,N+1).

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Contributors:
	   Jeff Rutter, Computer Science Division, University of California at Berkeley, USA
	    Modified by Francoise Tisseur, University of Tennessee
	    Modified description of INFO. Sven, 16 Feb 05.

       Definition at line 183 of file ssyevd.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      ssyevd.f(3)


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