Developer Reference

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

p?sytd2/p?hetd2

Reduces a symmetric/Hermitian matrix to real symmetric tridiagonal form by an orthogonal/unitary similarity transformation (local unblocked algorithm).

Syntax

call pssytd2
(
uplo
,
n
,
a
,
ia
,
ja
,
desca
,
d
,
e
,
tau
,
work
,
lwork
,
info
)
call pdsytd2
(
uplo
,
n
,
a
,
ia
,
ja
,
desca
,
d
,
e
,
tau
,
work
,
lwork
,
info
)
call pchetd2
(
uplo
,
n
,
a
,
ia
,
ja
,
desca
,
d
,
e
,
tau
,
work
,
lwork
,
info
)
call pzhetd2
(
uplo
,
n
,
a
,
ia
,
ja
,
desca
,
d
,
e
,
tau
,
work
,
lwork
,
info
)
Description
The
p?sytd2/p?hetd2
routine
reduces a real symmetric/complex Hermitian matrix sub(
A
) to symmetric/Hermitian tridiagonal form
T
by an orthogonal/unitary similarity transformation:
Q'
*sub(
A
)*
Q
=
T
, where
sub(
A
) =
A
(
ia
:
ia
+
n
-1
,
ja
:
ja
+
n
-1)
.
Input Parameters
uplo
(global)
CHARACTER
.
Specifies whether the upper or lower triangular part of the symmetric/Hermitian matrix sub(
A
) is stored:
=
'U'
: upper triangular
=
'L'
: lower triangular
n
(global)
INTEGER
.
The number of rows and columns to be operated on, that is, the order of the distributed matrix sub(
A
).
n
0
.
a
(local)
REAL
for
pssytd2
DOUBLE PRECISION
for
pdsytd2
COMPLEX
for
pchetd2
COMPLEX*16
for
pzhetd2
.
Pointer into the local memory to an array of size
(
lld_a
,
LOC
c
(
ja
+
n
-1))
.
On entry, this array contains the local pieces of the
n
-by-
n
symmetric/Hermitian distributed matrix sub(
A
).
If
uplo
=
'U'
, the leading
n
-by-
n
upper triangular part of sub(
A
) contains the upper triangular part of the matrix, and the strictly lower triangular part of sub(
A
) is not referenced.
If
uplo
=
'L'
, the leading
n
-by-
n
lower triangular part of sub(
A
) contains the lower triangular part of the matrix, and the strictly upper triangular part of sub(
A
) is not referenced.
ia