cgemlq.f(3) LAPACK cgemlq.f(3)

cgemlq.f


subroutine cgemlq (SIDE, TRANS, M, N, K, A, LDA, T, TSIZE, C, LDC, WORK, LWORK, INFO)
CGEMLQ

CGEMLQ

Purpose:

CGEMLQ overwrites the general real M-by-N matrix C with
                 SIDE = 'L'     SIDE = 'R'
 TRANS = 'N':      Q * C          C * Q
 TRANS = 'C':      Q**H * C       C * Q**H
 where Q is a complex unitary matrix defined as the product
 of blocked elementary reflectors computed by short wide
 LQ factorization (CGELQ)

Parameters

SIDE
SIDE is CHARACTER*1
= 'L': apply Q or Q**H from the Left;
= 'R': apply Q or Q**H from the Right.

TRANS

TRANS is CHARACTER*1
= 'N':  No transpose, apply Q;
= 'C':  Conjugate transpose, apply Q**H.

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 C. N >= 0.

K

K is INTEGER
The number of elementary reflectors whose product defines
the matrix Q.
If SIDE = 'L', M >= K >= 0;
if SIDE = 'R', N >= K >= 0.

A

A is COMPLEX array, dimension
                     (LDA,M) if SIDE = 'L',
                     (LDA,N) if SIDE = 'R'
Part of the data structure to represent Q as returned by CGELQ.

LDA

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

T

T is COMPLEX array, dimension (MAX(5,TSIZE)).
Part of the data structure to represent Q as returned by CGELQ.

TSIZE

TSIZE is INTEGER
The dimension of the array T. TSIZE >= 5.

C

C is COMPLEX array, dimension (LDC,N)
On entry, the M-by-N matrix C.
On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.

LDC

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

WORK

(workspace) COMPLEX array, dimension (MAX(1,LWORK))

LWORK

LWORK is INTEGER
The dimension of the array WORK.
If LWORK = -1, then a workspace query is assumed. The routine
only calculates the size of the WORK array, returns this
value as WORK(1), and no error message related to WORK 
is issued by XERBLA.

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

These details are particular for this LAPACK implementation. Users should not 
take them for granted. These details may change in the future, and are not likely
true for another LAPACK implementation. These details are relevant if one wants
to try to understand the code. They are not part of the interface.
In this version,
         T(2): row block size (MB)
         T(3): column block size (NB)
         T(6:TSIZE): data structure needed for Q, computed by
                          CLASWQR or CGELQT
 Depending on the matrix dimensions M and N, and row and column
 block sizes MB and NB returned by ILAENV, CGELQ will use either
 CLASWLQ (if the matrix is wide-and-short) or CGELQT to compute
 the LQ factorization.
 This version of CGEMLQ will use either CLAMSWLQ or CGEMLQT to 
 multiply matrix Q by another matrix.
 Further Details in CLAMSWLQ or CGEMLQT.

Definition at line 168 of file cgemlq.f.

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