Developer Reference

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

?gbequ

Computes row and column scaling factors intended to equilibrate a banded matrix and reduce its condition number.

Syntax

call sgbequ
(
m
,
n
,
kl
,
ku
,
ab
,
ldab
,
r
,
c
,
rowcnd
,
colcnd
,
amax
,
info
)
call dgbequ
(
m
,
n
,
kl
,
ku
,
ab
,
ldab
,
r
,
c
,
rowcnd
,
colcnd
,
amax
,
info
)
call cgbequ
(
m
,
n
,
kl
,
ku
,
ab
,
ldab
,
r
,
c
,
rowcnd
,
colcnd
,
amax
,
info
)
call zgbequ
(
m
,
n
,
kl
,
ku
,
ab
,
ldab
,
r
,
c
,
rowcnd
,
colcnd
,
amax
,
info
)
call gbequ
(
ab
,
r
,
c
[
,
kl
]
[
,
rowcnd
]
[
,
colcnd
]
[
,
amax
]
[
,
info
]
)
Include Files
  • mkl.fi
    ,
    lapack.f90
Description
The routine computes row and column scalings intended to equilibrate an
m
-by-
n
band matrix
A
and reduce its condition number. The output array
r
returns the row scale factors and the array
c
the column scale factors. These factors are chosen to try to make the largest element in each row and column of the matrix
B
with elements
b
i
j
=
r
(i)*
a
i
j
*
c
(j)
have absolute value 1.
See
?laqgb
auxiliary function that uses scaling factors computed by
?gbequ
.
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
.
kl
INTEGER
.
The number of subdiagonals within the band of
A
;
kl
0
.