DSYEV_PF Subroutine

subroutine DSYEV_PF(JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, INFO)

\brief DSYEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for SY matrices \htmlonly Download DSYEV + dependencies [TGZ] [ZIP] [TXT] \endhtmlonly \par Purpose:

\verbatim

DSYEV computes all eigenvalues and, optionally, eigenvectors of a real symmetric matrix A. \endverbatim \param[in] JOBZ \verbatim JOBZ is CHARACTER*1 = 'N': Compute eigenvalues only; = 'V': Compute eigenvalues and eigenvectors. \endverbatim

\param[in] UPLO \verbatim UPLO is CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. \endverbatim

\param[in] N \verbatim N is INTEGER The order of the matrix A. N >= 0. \endverbatim

\param[in,out] A \verbatim A is 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 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. \endverbatim

\param[in] LDA \verbatim LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N). \endverbatim

\param[out] W \verbatim W is DOUBLE PRECISION array, dimension (N) If INFO = 0, the eigenvalues in ascending order. \endverbatim

\param[out] WORK \verbatim WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK. \endverbatim

\param[in] LWORK \verbatim LWORK is INTEGER The length of the array WORK. LWORK >= max(1,3N-1). For optimal efficiency, LWORK >= (NB+2)N, where NB is the blocksize for DSYTRD 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.

\endverbatim

\param[out] INFO \verbatim INFO is 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. \endverbatim \author Univ. of Tennessee \author Univ. of California Berkeley \author Univ. of Colorado Denver \author NAG Ltd. \date December 2016 \ingroup doubleSYeigen

Arguments