Contents

# ?dttrsb

Solves a system of linear equations with a diagonally dominant tridiagonal coefficient matrix using the LU factorization computed by
?dttrfb
.

## Syntax

Include Files
• mkl.h
Description
The
?dttrsb
routine solves the following systems of linear equations with multiple right hand sides for
X
:
A
*
X
=
B
if
trans
=
'N'
,
A
T
*
X
=
B
if
trans
=
'T'
,
A
H
*
X
=
B
if
trans
=
'C'
(for complex matrices only).
Before calling this routine, call
?dttrfb
to compute the factorization of
A
.
Input Parameters
trans
Must be
'N'
or
'T'
or
'C'
.
Indicates the form of the equations solved for
X
:
If
trans
=
'N'
, then
A
*
X
=
B
.
If
trans
=
'T'
, then
A
T
*
X
=
B
.
If
trans
=
'C'
, then
A
H
*
X
=
B
.
n
The order of
A
;
n
0.
nrhs
The number of right-hand sides, that is, the number of columns in
B
;
nrhs
0.
dl
,
d
,
du
Arrays:
dl
(
n
-1)
,
d
(
n
)
,
du
(
n
-1)
.
The array
dl
contains the
(
n
- 1)
multipliers that define the matrices
L
1
,
L
2
from the factorization of
A
.
The array
d
contains the
n
diagonal elements of the upper triangular matrix
U
from the factorization of
A
.
The array
du
contains the (
n
- 1) elements of the superdiagonal of
U
.
b
Array of size max(1,
ldb
*
nrhs
). Contains the matrix
B
whose columns are the right-hand sides for the systems of equations.
ldb
b
;
ldb
max(1,
n
)
.
Output Parameters
b
Overwritten by the solution matrix
X
.
info
If
info
= 0
, the execution is successful.
If
info
=
-i
, the
i
-th parameter had an illegal value.

#### Product and Performance Information

1

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