NAME

SYNOPSIS

  SUBROUTINE DGEQPF( M, N, A, LDA, JPIVOT, TAU, WORK, INFO)
  INTEGER M, N, LDA, INFO
  INTEGER JPIVOT(*)
  DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
 
  SUBROUTINE DGEQPF_64( M, N, A, LDA, JPIVOT, TAU, WORK, INFO)
  INTEGER*8 M, N, LDA, INFO
  INTEGER*8 JPIVOT(*)
  DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
 

F95 INTERFACE

  SUBROUTINE GEQPF( [M], [N], A, [LDA], JPIVOT, TAU, [WORK], [INFO])
  INTEGER :: M, N, LDA, INFO
  INTEGER, DIMENSION(:) :: JPIVOT
  REAL(8), DIMENSION(:) :: TAU, WORK
  REAL(8), DIMENSION(:,:) :: A
 
  SUBROUTINE GEQPF_64( [M], [N], A, [LDA], JPIVOT, TAU, [WORK], [INFO])
  INTEGER(8) :: M, N, LDA, INFO
  INTEGER(8), DIMENSION(:) :: JPIVOT
  REAL(8), DIMENSION(:) :: TAU, WORK
  REAL(8), DIMENSION(:,:) :: A
 

C INTERFACE

void dgeqpf(int m, int n, double *a, int lda, int *jpivot, double *tau, int *info);

void dgeqpf_64(long m, long n, double *a, long lda, long *jpivot, double *tau, long *info);

PURPOSE

SGEQPF computes a QR factorization with column pivoting of a real M-by-N matrix A: A*P = Q*R.

ARGUMENTS

* M (input)

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

* N (input)

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

* A (input/output)

On entry, the M-by-N matrix A. On exit, the upper triangle of the array contains the min(M,N)-by-N upper triangular matrix R; the elements below the diagonal, together with the array TAU, represent the orthogonal matrix Q as a product of min(m,n) elementary reflectors.

* LDA (input)

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

* JPIVOT (input)

On entry, if JPIVOT(i) .ne. 0, the i-th column of A is permuted to the front of A*P (a leading column); if JPIVOT(i) = 0, the i-th column of A is a free column. On exit, if JPIVOT(i) = k, then the i-th column of A*P was the k-th column of A.

* TAU (output)

The scalar factors of the elementary reflectors.

* WORK (workspace)

dimension(N)

* INFO (output)