NAME

SYNOPSIS

  SUBROUTINE CHETRD( UPLO, N, A, LDA, D, E, TAU, WORK, LWORK, INFO)
  CHARACTER * 1 UPLO
  COMPLEX A(LDA,*), TAU(*), WORK(*)
  INTEGER N, LDA, LWORK, INFO
  REAL D(*), E(*)
 
  SUBROUTINE CHETRD_64( UPLO, N, A, LDA, D, E, TAU, WORK, LWORK, INFO)
  CHARACTER * 1 UPLO
  COMPLEX A(LDA,*), TAU(*), WORK(*)
  INTEGER*8 N, LDA, LWORK, INFO
  REAL D(*), E(*)
 

F95 INTERFACE

  SUBROUTINE HETRD( UPLO, [N], A, [LDA], D, E, TAU, [WORK], [LWORK], 
 *       [INFO])
  CHARACTER(LEN=1) :: UPLO
  COMPLEX, DIMENSION(:) :: TAU, WORK
  COMPLEX, DIMENSION(:,:) :: A
  INTEGER :: N, LDA, LWORK, INFO
  REAL, DIMENSION(:) :: D, E
 
  SUBROUTINE HETRD_64( UPLO, [N], A, [LDA], D, E, TAU, [WORK], [LWORK], 
 *       [INFO])
  CHARACTER(LEN=1) :: UPLO
  COMPLEX, DIMENSION(:) :: TAU, WORK
  COMPLEX, DIMENSION(:,:) :: A
  INTEGER(8) :: N, LDA, LWORK, INFO
  REAL, DIMENSION(:) :: D, E
 

C INTERFACE

void chetrd(char uplo, int n, complex *a, int lda, float *d, float *e, complex *tau, int *info);

void chetrd_64(char uplo, long n, complex *a, long lda, float *d, float *e, complex *tau, long *info);

PURPOSE

ARGUMENTS

* UPLO (input)

* N (input)

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

* A (input)

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, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit, if UPLO = 'U', the diagonal and first superdiagonal of A are overwritten by the corresponding elements of the tridiagonal matrix T, and the elements above the first superdiagonal, with the array TAU, represent the unitary matrix Q as a product of elementary reflectors; if UPLO

* LDA (input)

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

* D (output)

The diagonal elements of the tridiagonal matrix T: D(i) = A(i,i).

* E (output)

The off-diagonal elements of the tridiagonal matrix T: E(i) = A(i,i+1) if UPLO = 'U', E(i) = A(i+1,i) if UPLO = 'L'.

* TAU (output)

The scalar factors of the elementary reflectors (see Further Details).

* WORK (workspace)

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

* LWORK (input)

The dimension of the array WORK. LWORK >= 1. For optimum performance LWORK >= N*NB, where NB is the optimal blocksize.

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.

* INFO (output)