Developer Reference

  • 2020.2
  • 07/15/2020
  • Public Content
Contents

p?labrd

Reduces the first
nb
rows and columns of a general rectangular matrix A to real bidiagonal form by an orthogonal/unitary transformation, and returns auxiliary matrices that are needed to apply the transformation to the unreduced part of A.

Syntax

call pslabrd
(
m
,
n
,
nb
,
a
,
ia
,
ja
,
desca
,
d
,
e
,
tauq
,
taup
,
x
,
ix
,
jx
,
descx
,
y
,
iy
,
jy
,
descy
,
work
)
call pdlabrd
(
m
,
n
,
nb
,
a
,
ia
,
ja
,
desca
,
d
,
e
,
tauq
,
taup
,
x
,
ix
,
jx
,
descx
,
y
,
iy
,
jy
,
descy
,
work
)
call pclabrd
(
m
,
n
,
nb
,
a
,
ia
,
ja
,
desca
,
d
,
e
,
tauq
,
taup
,
x
,
ix
,
jx
,
descx
,
y
,
iy
,
jy
,
descy
,
work
)
call pzlabrd
(
m
,
n
,
nb
,
a
,
ia
,
ja
,
desca
,
d
,
e
,
tauq
,
taup
,
x
,
ix
,
jx
,
descx
,
y
,
iy
,
jy
,
descy
,
work
)
Description
The
p?labrd
routine
reduces the first
nb
rows and columns of a real/complex general
m
-by-
n
distributed matrix sub(
A
) =
A
(
ia
:
ia
+
m
-1
,
ja
:
ja
+
n
-1)
to upper or lower bidiagonal form by an orthogonal/unitary transformation
Q'* A * P
, and returns the matrices
X
and
Y
necessary to apply the transformation to the unreduced part of sub(
A
).
If
m
n
,
sub(
A
)
is reduced to upper bidiagonal form; if
m
<
n
,
sub(
A
)
is reduced to lower bidiagonal form.
This is an auxiliary
routine
called by
p?gebrd
.
Input Parameters
m
(global)
INTEGER
.
The number of rows in the distributed matrix
sub(
A
)
.
(
m
0)
.
n
(global)
INTEGER
.
The number of columns in the distributed matrix sub(
A
).
(
n
0)
.
nb
(global)
INTEGER
.
The number of leading rows and columns of sub(
A
) to be reduced.
a
(local).
REAL
for
pslabrd
DOUBLE PRECISION
for
pdlabrd
COMPLEX
for
pclabrd