Developer Reference

Contents

?ungrq

Generates the complex matrix Q of the RQ factorization formed by
?gerqf
.

Syntax

lapack_int
LAPACKE_cungrq
(
int
matrix_layout
,
lapack_int
m
,
lapack_int
n
,
lapack_int
k
,
lapack_complex_float
*
a
,
lapack_int
lda
,
const
lapack_complex_float
*
tau
);
lapack_int
LAPACKE_zungrq
(
int
matrix_layout
,
lapack_int
m
,
lapack_int
n
,
lapack_int
k
,
lapack_complex_double
*
a
,
lapack_int
lda
,
const
lapack_complex_double
*
tau
);
Include Files
  • mkl.h
Description
The routine generates an
m
-by-
n
complex matrix with orthonormal rows, which is defined as the last
m
rows of a product of
k
elementary reflectors
H
(
i
)
of order
n
:
Q
=
H
(1)
H
*
H
(2)
H
*...*
H
(
k
)
H
as returned by the routines gerqf. Use this routine after a call to
cgerqf
/
zgerqf
.
Input Parameters
matrix_layout
Specifies whether matrix storage layout is row major (
LAPACK_ROW_MAJOR
) or column major (
LAPACK_COL_MAJOR
).
m
The number of rows of the matrix
Q
(
m
0
).
n
The number of columns of the matrix
Q
(
n
m
).
k
The number of elementary reflectors whose product defines the matrix
Q
(
m
k
0
).
a
,
tau
Arrays:
a
(size max(1,
lda
*
n
) for column major layout and max(1,
lda
*
m
) for row major layout)
,
tau
.
On entry, the (
m
-
k
+
i
)th row of
a
must contain the vector which defines the elementary reflector
H
(
i
), for i = 1,2,...,
k
, as returned by
cgerqf
/
zgerqf
in the last
k
rows of its array argument
a
;
tau
[
i
- 1]
must contain the scalar factor of the elementary reflector
H
(
i
), as returned by
cgerqf
/
zgerqf
;
The size of
tau
must be at least max(1,
k
).
lda
The leading dimension of
a
; at least max(1,
m
)
for column major layout and max(1,
n
) for row major layout
.
Output Parameters
a
Overwritten by the
m
last rows of the
n
-by-
n
unitary matrix
Q
.
Return Values
This function returns a value
info
.
If
info
=0
, the execution is successful.
If
info
=
-i
, the
i
-th parameter had an illegal value.
Application Notes
The real counterpart of this routine is orgrq.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.