cheev (3)

Functions/Subroutines

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

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

subroutine cheev (characterJOBZ, characterUPLO, integerN, complex, dimension( lda, * )A, integerLDA, real, dimension( * )W, complex, dimension( * )WORK, integerLWORK, real, dimension( * )RWORK, integerINFO)

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

Purpose:

 CHEEV computes all eigenvalues and, optionally, eigenvectors of a
 complex Hermitian matrix A.

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 COMPLEX 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.

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

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 CHETRD 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.

RWORK

          RWORK is REAL array, dimension (max(1, 3*N-2))

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.

Date:

November 2011

Definition at line 140 of file cheev.f.

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