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 zgeqr2p.f(3) LAPACK zgeqr2p.f(3)

zgeqr2p.f -

# SYNOPSIS

## Functions/Subroutines

subroutine zgeqr2p (M, N, A, LDA, TAU, WORK, INFO)

ZGEQR2P computes the QR factorization of a general rectangular matrix with non-negative diagonal elements using an unblocked algorithm.

# Function/Subroutine Documentation

## subroutine zgeqr2p (integerM, integerN, complex*16, dimension( lda, * )A, integerLDA, complex*16, dimension( * )TAU, complex*16, dimension( * )WORK, integerINFO)

ZGEQR2P computes the QR factorization of a general rectangular matrix with non-negative diagonal elements using an unblocked algorithm.
Purpose:
``` ZGEQR2P computes a QR factorization of a complex m by n matrix A:
A = 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 COMPLEX*16 array, dimension (LDA,N)
On entry, the m by n matrix A.
On exit, the elements on and above the diagonal of the array
contain the min(m,n) by n upper trapezoidal matrix R (R is
upper triangular if m >= n); the elements below the diagonal,
with the array TAU, represent the unitary matrix Q as a
product of elementary reflectors (see Further Details).
```
LDA
```          LDA is INTEGER
The leading dimension of the array A.  LDA >= max(1,M).
```
TAU
```          TAU is COMPLEX*16 array, dimension (min(M,N))
The scalar factors of the elementary reflectors (see Further
Details).
```
WORK
```          WORK is COMPLEX*16 array, dimension (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
NAG Ltd.
Date:
September 2012
Further Details:
```  The matrix Q is represented as a product of elementary reflectors

Q = H(1) H(2) . . . H(k), where k = min(m,n).

Each H(i) has the form

H(i) = I - tau * v * v**H

where tau is a complex scalar, and v is a complex 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),
and tau in TAU(i).
```
Definition at line 122 of file zgeqr2p.f.

# Author

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