Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

?ungql

Generates the complex matrix Q of the QL factorization formed by
?geqlf
.

Syntax

lapack_int
LAPACKE_cungql
(
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_zungql
(
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
Q
 with orthonormal columns, which is defined as the last
n
 columns of a product of
k
 elementary reflectors
H
(
i
)
 of order
m
:
Q
 =
H
(
k
)
 *...*
H
(2)
*
H
(1)
 as returned by the routines geqlf/geqlf . Use this routine after a call to
cgeqlf
/
zgeqlf
.
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
 (
m
≥
n
≥
0
).
k
The number of elementary reflectors whose product defines the matrix
Q
 (
n
≥
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 (
n
 -
k
 +
i
)th column of
a
 must contain the vector which defines the elementary reflector
H
(
i
), for i = 1,2,...,
k
, as returned by
cgeqlf
/
zgeqlf
 in the last
k
 columns of its array argument
a
;
tau
[
i
- 1]
 must contain the scalar factor of the elementary reflector
H
(
i
), as returned by
cgeqlf
/
zgeqlf
;
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 last
n
 columns of the
m
-by-
m
 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 orgql.

Product and Performance Information

1

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