NAME

SYNOPSIS

  SUBROUTINE DGEBRD( M, N, A, LDA, D, E, TAUQ, TAUP, WORK, LWORK, 
 *      INFO)
  INTEGER M, N, LDA, LWORK, INFO
  DOUBLE PRECISION A(LDA,*), D(*), E(*), TAUQ(*), TAUP(*), WORK(*)
 
  SUBROUTINE DGEBRD_64( M, N, A, LDA, D, E, TAUQ, TAUP, WORK, LWORK, 
 *      INFO)
  INTEGER*8 M, N, LDA, LWORK, INFO
  DOUBLE PRECISION A(LDA,*), D(*), E(*), TAUQ(*), TAUP(*), WORK(*)
 

F95 INTERFACE

  SUBROUTINE GEBRD( [M], [N], A, [LDA], D, E, TAUQ, TAUP, [WORK], 
 *       [LWORK], [INFO])
  INTEGER :: M, N, LDA, LWORK, INFO
  REAL(8), DIMENSION(:) :: D, E, TAUQ, TAUP, WORK
  REAL(8), DIMENSION(:,:) :: A
 
  SUBROUTINE GEBRD_64( [M], [N], A, [LDA], D, E, TAUQ, TAUP, [WORK], 
 *       [LWORK], [INFO])
  INTEGER(8) :: M, N, LDA, LWORK, INFO
  REAL(8), DIMENSION(:) :: D, E, TAUQ, TAUP, WORK
  REAL(8), DIMENSION(:,:) :: A
 

C INTERFACE

void dgebrd(int m, int n, double *a, int lda, double *d, double *e, double *tauq, double *taup, int *info);

void dgebrd_64(long m, long n, double *a, long lda, double *d, double *e, double *tauq, double *taup, long *info);

PURPOSE

If m >= n, B is upper bidiagonal; if m < n, B is lower bidiagonal.

ARGUMENTS

* M (input)

The number of rows in the matrix A. M >= 0.

* N (input)

The number of columns in the matrix A. N >= 0.

* A (input/output)

On entry, the M-by-N general matrix to be reduced. On exit, if m >= n, the diagonal and the first superdiagonal are overwritten with the upper bidiagonal matrix B; the elements below the diagonal, with the array TAUQ, represent the orthogonal matrix Q as a product of elementary reflectors, and the elements above the first superdiagonal, with the array TAUP, represent the orthogonal matrix P as a product of elementary reflectors; if m < n, the diagonal and the first subdiagonal are overwritten with the lower bidiagonal matrix B; the elements below the first subdiagonal, with the array TAUQ, represent the orthogonal matrix Q as a product of elementary reflectors, and the elements above the diagonal, with the array TAUP, represent the orthogonal matrix P as a product of elementary reflectors. See Further Details.

* LDA (input)

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

* D (output)

The diagonal elements of the bidiagonal matrix B: D(i) = A(i,i).

* E (output)

The off-diagonal elements of the bidiagonal matrix B: if m >= n, E(i) = A(i,i+1) for i = 1,2,...,n-1; if m < n, E(i) = A(i+1,i) for i = 1,2,...,m-1.

* TAUQ (output)

The scalar factors of the elementary reflectors which represent the orthogonal matrix Q. See Further Details.

* TAUP (output)

The scalar factors of the elementary reflectors which represent the orthogonal matrix P. See Further Details.

* WORK (workspace)

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

* LWORK (input)

The length of the array WORK. LWORK >= max(1,M,N). For optimum performance LWORK >= (M+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)