NAME

SYNOPSIS

  SUBROUTINE SSYTRD( UPLO, N, A, LDA, D, E, TAU, WORK, LWORK, INFO)
  CHARACTER * 1 UPLO
  INTEGER N, LDA, LWORK, INFO
  REAL A(LDA,*), D(*), E(*), TAU(*), WORK(*)
 
  SUBROUTINE SSYTRD_64( UPLO, N, A, LDA, D, E, TAU, WORK, LWORK, INFO)
  CHARACTER * 1 UPLO
  INTEGER*8 N, LDA, LWORK, INFO
  REAL A(LDA,*), D(*), E(*), TAU(*), WORK(*)
 

F95 INTERFACE

  SUBROUTINE SYTRD( UPLO, N, A, [LDA], D, E, TAU, [WORK], [LWORK], 
 *       [INFO])
  CHARACTER(LEN=1) :: UPLO
  INTEGER :: N, LDA, LWORK, INFO
  REAL, DIMENSION(:) :: D, E, TAU, WORK
  REAL, DIMENSION(:,:) :: A
 
  SUBROUTINE SYTRD_64( UPLO, N, A, [LDA], D, E, TAU, [WORK], [LWORK], 
 *       [INFO])
  CHARACTER(LEN=1) :: UPLO
  INTEGER(8) :: N, LDA, LWORK, INFO
  REAL, DIMENSION(:) :: D, E, TAU, WORK
  REAL, DIMENSION(:,:) :: A
 

C INTERFACE

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

void ssytrd_64(char uplo, long n, float *a, long lda, float *d, float *e, float *tau, long *info);

PURPOSE

ARGUMENTS

* UPLO (input)

* N (input)

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

* A (input)

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, 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 orthogonal 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)