---
name: "sgeqpf.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/sgeqpf.f"
---

# sgeqpf.f(3)

## NAME

SRC/DEPRECATED/sgeqpf.f

## SYNOPSIS

### Functions/Subroutines

subroutine **sgeqpf** (m, n, a, lda, jpvt, tau, work, info)\
 **SGEQPF**

## Function/Subroutine Documentation

### subroutine sgeqpf (integer m, integer n, real, dimension( lda, \* ) a, integer lda, integer, dimension( \* ) jpvt, real, dimension( \* ) tau, real, dimension( \* ) work, integer info)

**SGEQPF**

**Purpose:**

```
!>
!> This routine is deprecated and has been replaced by routine SGEQP3.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.
!>
```

**Parameters**

*M*

```
!>          M is INTEGER
!>          The number of rows of the matrix A. M >= 0.
!>
```

*N*

```
!>          N is INTEGER
!>          The number of columns of the matrix A. N >= 0
!>
```

*A*

```
!>          A is REAL array, dimension (LDA,N)
!>          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*

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

*JPVT*

```
!>          JPVT is INTEGER array, dimension (N)
!>          On entry, if JPVT(i) .ne. 0, the i-th column of A is permuted
!>          to the front of A*P (a leading column); if JPVT(i) = 0,
!>          the i-th column of A is a free column.
!>          On exit, if JPVT(i) = k, then the i-th column of A*P
!>          was the k-th column of A.
!>
```

*TAU*

```
!>          TAU is REAL array, dimension (min(M,N))
!>          The scalar factors of the elementary reflectors.
!>
```

*WORK*

```
!>          WORK is REAL array, dimension (3*N)
!>
```

*INFO*

```
!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**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**T
!>
!>  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.
!>
!>  Partial column norm updating strategy modified by
!>    Z. Drmac and Z. Bujanovic, Dept. of Mathematics,
!>    University of Zagreb, Croatia.
!>  -- April 2011                                                      --
!>  For more details see LAPACK Working Note 176.
!>
```

Definition at line **141** of file **sgeqpf.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.