cheev-f(3)

cheev.f –

Synopsis

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

Function/Subroutine Documentation

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

 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 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.

Author

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