DORGQR (3) Linux Manual Page

dorgqr.f –

Synopsis

Functions/Subroutines

subroutine dorgqr (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
DORGQR

Function/Subroutine Documentation

subroutine dorgqr (integerM, integerN, integerK, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )TAU, double precision, dimension( * )WORK, integerLWORK, integerINFO)

DORGQR

Purpose:

 DORGQR generates an M-by-N real matrix Q with orthonormal columns,

 which is defined as the first N columns of a product of K elementary

 reflectors of order M

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

 as returned by DGEQRF.

 

Parameters:

M

 M is INTEGER

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

N

 N is INTEGER

 The number of columns of the matrix Q. M >= N >= 0.

K

 K is INTEGER

 The number of elementary reflectors whose product defines the

 matrix Q. N >= K >= 0.

A

 A is DOUBLE PRECISION array, dimension (LDA,N)

 On entry, the i-th column must contain the vector which

 defines the elementary reflector H(i), for i = 1,2,…,k, as

 returned by DGEQRF in the first k columns of its array

 argument A.

 On exit, the M-by-N matrix Q.

LDA

 LDA is INTEGER

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

TAU

 TAU is DOUBLE PRECISION array, dimension (K)

 TAU(i) must contain the scalar factor of the elementary

 reflector H(i), as returned by DGEQRF.

WORK

 WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))

 On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK

 LWORK is INTEGER

 The dimension of the array WORK. LWORK >= max(1,N).

 For optimum performance LWORK >= N*NB, where NB is the

 optimal blocksize.

 If LWORK = -1, then a workspace query is assumed; the routine

 only calculates the optimal size of the WORK array, returns

 this value as the first entry of the WORK array, and no error

 message related to LWORK is issued by XERBLA.

INFO

 INFO is INTEGER

 = 0: successful exit

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

 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Definition at line 129 of file dorgqr.f.

Author

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