cungrq-f(3)

cungrq.f –

Synopsis

Functions/Subroutines

subroutine cungrq (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
CUNGRQ

Function/Subroutine Documentation

subroutine cungrq (integerM, integerN, integerK, complex, dimension( lda, * )A, integerLDA, complex, dimension( * )TAU, complex, dimension( * )WORK, integerLWORK, integerINFO)

CUNGRQ

Purpose:

 CUNGRQ generates an M-by-N complex matrix Q with orthonormal rows,
 which is defined as the last M rows of a product of K elementary
 reflectors of order N
 Q = H(1)**H H(2)**H . . . H(k)**H
 as returned by CGERQF.

Parameters:

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

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

 K is INTEGER
 The number of elementary reflectors whose product defines the
 matrix Q. M >= K >= 0.

 A is COMPLEX array, dimension (LDA,N)
 On entry, the (m-k+i)-th row must contain the vector which
 defines the elementary reflector H(i), for i = 1,2,...,k, as
 returned by CGERQF in the last k rows 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 COMPLEX array, dimension (K)
 TAU(i) must contain the scalar factor of the elementary
 reflector H(i), as returned by CGERQF.

WORK

 WORK is COMPLEX 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,M).
 For optimum performance LWORK >= M*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 cungrq.f.

Author

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