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## zheev()

subroutine zheev | ( | character | jobz,
|  | character | uplo,
|  | integer | n,
|  | complex*16, dimension( lda, * ) | a,
|  | integer | lda,
|  | double precision, dimension( * ) | w,
|  | complex*16, dimension( * ) | work,
|  | integer | lwork,
|  | double precision, dimension( * ) | rwork,
|  | integer | info )

ZHEEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for HE matrices

Download ZHEEV + dependencies [TGZ] [ZIP] [TXT]

Purpose:

      !>
      !> ZHEEV computes all eigenvalues and, optionally, eigenvectors of a
      !> complex Hermitian matrix A.
      !>

Parameters

  [in]

  JOBZ

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

  [in]

  UPLO

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

  [in]

  N

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

  [in,out]

  A

      !>          A is COMPLEX*16 array, dimension (LDA, N)
      !>          On entry, the Hermitian 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.
      !>

  [in]

  LDA

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

  [out]

  W

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

  [out]

  WORK

      !>          WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
      !>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
      !>

  [in]

  LWORK

      !>          LWORK is INTEGER
      !>          The length of the array WORK.  LWORK >= max(1,2*N-1).
      !>          For optimal efficiency, LWORK >= (NB+1)*N,
      !>          where NB is the blocksize for ZHETRD 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.
      !>

  [out]

  RWORK

      !>          RWORK is DOUBLE PRECISION array, dimension (max(1, 3*N-2))
      !>

  [out]

  INFO

      !>          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.
      !>

Author
  Univ. of Tennessee
  Univ. of California Berkeley
  Univ. of Colorado Denver
  NAG Ltd.