Developer Reference

  • 098
  • 03/30/2020
  • Public Content
Contents

?gelq

Computes an LQ factorization of a general matrix.
call sgelq
(
m
,
n
,
a
,
lda
,
t
,
tsize
,
work
,
lwork
,
info
)
call dgelq
(
m
,
n
,
a
,
lda
,
t
,
tsize
,
work
,
lwork
,
info
)
call cgelq
(
m
,
n
,
a
,
lda
,
t
,
tsize
,
work
,
lwork
,
info
)
call zgelq
(
m
,
n
,
a
,
lda
,
t
,
tsize
,
work
,
lwork
,
info
)
Description
The
?gelq
routines computes an LQ factorization of an
m
-by-
n
matrix
A
. If the matrix is short and wide (
n
is substantially larger than
m
), a highly scalable algorithm is used to avoid communication overhead.
The internal format of the elementary reflectors generated by
?gelq
is only compatible with the
?gemlq
routine and not any other LQ routines.
An optimized version of
?gelq
is not available.
Input Parameters
m
INTEGER
.
The number of rows of the matrix
A
.
m
0.
n
INTEGER
.
The number of columns of the matrix
A
.
n
0.
a
REAL
for
sgelq
DOUBLE PRECISION
for
dgelq
COMPLEX
for
cgelq
COMPLEX*16
for
zgelq
Array, size
(
lda
,
n
)
. Contains the
m
-by-
n
matrix
A
.
lda
INTEGER
.
The leading dimension of the array
a
.
lda
max(1,
m
)
.
tsize
INTEGER
.
If
tsize
5, the size of the array
t
. If
tsize
= -1 or
tsize
= -2, then the routine performs a workspace query. The routine calculates the sizes required for the
t
and
work
arrays and returns these values as the first entries of the
t
and
work
arrays, without issuing any error message related to
t
or
work
by
xerbla
.
If
tsize
= -1, the routine calculates the optimal size of
t
for optimum performance and returns this value in
t
(1)
.
If
tsize
= -2, the routine calculates then minimum size required for
t
and returns this value in
t
(1)
.
lwork
INTEGER
.
The size of the array
work
. If
lwork
= -1 or
lwork
= -2, then the routine performs a workspace query. The routine only calculates the sizes of the
t
and
work
arrays and returns these values as the first entries of the
t
and
work
arrays, without issuing any error message related to
t
or
work
by
xerbla
.
If
lwork
= -1, the routine calculates the optimal size of
work
for optimum performance and returns this value in
work
(1)
.
If
lwork
= -2, the routine calculates the minimum size required for
work
and returns this value in
work
(1)
.
Output Parameters
a
REAL
for
sgelq
DOUBLE PRECISION
for
dgelq