Developer Reference

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

?langt

Returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of a general tridiagonal matrix.

Syntax

val
=
slangt
(
norm
,
n
,
dl
,
d
,
du
)
val
=
dlangt
(
norm
,
n
,
dl
,
d
,
du
)
val
=
clangt
(
norm
,
n
,
dl
,
d
,
du
)
val
=
zlangt
(
norm
,
n
,
dl
,
d
,
du
)
Include Files
  • mkl.fi
Description
The routine returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real/complex tridiagonal matrix
A
.
Input Parameters
norm
CHARACTER*1
. Specifies the value to be returned by the routine:
=
'M'
or
'm':
val
=
max
(
abs
(
A
i
j
)), largest absolute value of the matrix
A
.
=
'1'
or
'O'
or
'o':
val
=
norm1
(
A
), 1-norm of the matrix
A
(maximum column sum),
=
'I'
or
'i':
val
=
normI
(
A
), infinity norm of the matrix
A
(maximum row sum),
=
'F'
,
'f'
,
'E'
or
'e':
val
=
normF
(
A
), Frobenius norm of the matrix
A
(square root of sum of squares).
n
INTEGER
. The order of the matrix
A
.
n
0
. When
n
= 0
,
?langt
is set to zero.
dl
,
d
,
du
REAL
for
slangt
DOUBLE PRECISION
for
dlangt
COMPLEX
for
clangt
DOUBLE COMPLEX
for
zlangt
Arrays:
dl
(
n
-1),
d
(
n
),
du
(
n
-1).
The array
dl
contains the (
n
-1) sub-diagonal elements of
A
.
The array
d
contains the diagonal elements of
A
.
The array
du
contains the (
n
-1) super-diagonal elements of
A
.
Output Parameters
val
REAL
for
slangt
/
clangt
DOUBLE PRECISION
for
dlangt
/
zlangt
Value returned by the function.