## Developer Reference

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

# p?pttrsv

Solves a single triangular linear system via frontsolve or backsolve where the triangular matrix is a factor of a tridiagonal matrix computed by
p?pttrf
.

## Syntax

Description
The
p?pttrsv
routine
solves a tridiagonal triangular system of linear equations
A
(1:
n
,
ja
:
ja
+
n
-1)*
X
=
B
(
jb
:
jb+n
-1, 1:
nrhs
)
or
A
(1:
n
,
ja
:
ja
+
n
-1)
T
*
X
=
B
(
jb
:
jb+n
-1, 1:
nrhs
)
for real flavors,
A
(1:
n
,
ja
:
ja
+
n
-1)
H
*
X
=
B
(
jb
:
jb+n
-1, 1:
nrhs
)
for complex flavors,
where
A
(1:
n
,
ja
:
ja
+
n
-1)
is a tridiagonal triangular matrix factor produced by the Cholesky factorization code
p?pttrf
and is stored in
A
(1:
n
,
ja
:
ja
+
n
-1)
and
af
. The matrix stored in
A
(1:
n
,
ja
:
ja
+
n
-1)
is either upper or lower triangular according to
uplo
.
The routine
p?pttrf
must be called first.
Input Parameters
uplo
(global)
CHARACTER
.
Must be
'U'
or
'L'
.
If
uplo
=
'U'
, upper triangle of
A
(1:
n
,
ja
:
ja
+
n
-1)
is stored;
If
uplo
=
'L'
, lower triangle of
A
(1:
n
,
ja
:
ja
+
n
-1)
is stored.
trans
(global)
CHARACTER
.
Must be
'N'
or
'C'
.