sgeqrt2.f man page

sgeqrt2.f —

Synopsis

Functions/Subroutines

subroutine sgeqrt2 (M, N, A, LDA, T, LDT, INFO)
SGEQRT2 computes a QR factorization of a general real or complex matrix using the compact WY representation of Q.

Function/Subroutine Documentation

subroutine sgeqrt2 (integerM, integerN, real, dimension( lda, * )A, integerLDA, real, dimension( ldt, * )T, integerLDT, integerINFO)

SGEQRT2 computes a QR factorization of a general real or complex matrix using the compact WY representation of Q.

Purpose:

SGEQRT2 computes a QR factorization of a real M-by-N matrix A, 
using the compact WY representation of Q.

Parameters:

M

M is INTEGER
The number of rows of the matrix A.  M >= N.

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 real M-by-N matrix A.  On exit, the elements on and
above the diagonal contain the N-by-N upper triangular matrix R; the
elements below the diagonal are the columns of V.  See below for
further details.

LDA

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

T

T is REAL array, dimension (LDT,N)
The N-by-N upper triangular factor of the block reflector.
The elements on and above the diagonal contain the block
reflector T; the elements below the diagonal are not used.
See below for further details.

LDT

LDT is INTEGER
The leading dimension of the array T.  LDT >= max(1,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.

Date:

September 2012

Further Details:

The matrix V stores the elementary reflectors H(i) in the i-th column
below the diagonal. For example, if M=5 and N=3, the matrix V is

             V = (  1       )
                 ( v1  1    )
                 ( v1 v2  1 )
                 ( v1 v2 v3 )
                 ( v1 v2 v3 )

where the vi's represent the vectors which define H(i), which are returned
in the matrix A.  The 1's along the diagonal of V are not stored in A.  The
block reflector H is then given by

             H = I - V * T * V**T

where V**T is the transpose of V.

Definition at line 128 of file sgeqrt2.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

sgeqrt2(3) is an alias of sgeqrt2.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK