• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS
• FURTHER DETAILS

NAME

sgeqpf - routine is deprecated and has been replaced by routine SGEQP3

SYNOPSIS

  SUBROUTINE SGEQPF( M, N, A, LDA, JPIVOT, TAU, WORK, INFO)
  INTEGER M, N, LDA, INFO
  INTEGER JPIVOT(*)
  REAL A(LDA,*), TAU(*), WORK(*)

  SUBROUTINE SGEQPF_64( M, N, A, LDA, JPIVOT, TAU, WORK, INFO)
  INTEGER*8 M, N, LDA, INFO
  INTEGER*8 JPIVOT(*)
  REAL 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, DIMENSION(:) :: TAU, WORK
  REAL, DIMENSION(:,:) :: A

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

C INTERFACE

#include <sunperf.h>

void sgeqpf(int m, int n, float *a, int lda, int *jpivot, float *tau, int *info);

void sgeqpf_64(long m, long n, float *a, long lda, long *jpivot, float *tau, long *info);

PURPOSE

sgeqpf routine is deprecated and has been replaced by routine SGEQP3.

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)
  

   = 0:  successful exit

   < 0:  if INFO  = -i, the i-th argument had an illegal value

FURTHER DETAILS

The matrix Q is represented as a product of elementary reflectors

   Q  = H(1) H(2) . . . H(n)

Each H(i) has the form

   H  = I - tau * v * v'

where tau is a real scalar, and v is a real vector with

v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i).

The matrix P is represented in jpvt as follows: If

   jpvt(j)  = i

then the jth column of P is the ith canonical unit vector.