F06ZPF (ZHERK) (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual
NAG Library Routine Document
F06ZPF (ZHERK)
Note:
before using this routine, please read the Users' Note for your implementation to check the interpretation of
bold italicised
terms and other implementation-dependent details.
+
−
Contents
1
Purpose
2
Specification
3
Description
4
References
5
Parameters
6
Error Indicators and Warnings
7
Accuracy
8
Further Comments
9
Example
1 Purpose
F06ZPF (ZHERK) performs one of the Hermitian rank-
k
update operations
C
←
α
A
A
H
+
β
C
or
C
←
α
A
H
A
+
β
C
where
A
is a complex matrix,
C
is an
n
by
n
complex Hermitian matrix, and
α
and
β
are real scalars.
2 Specification
SUBROUTINE F06ZPF (
UPLO
,
TRANS
,
N
,
K
,
ALPHA
,
A
,
LDA
,
BETA
,
C
,
LDC
)
INTEGER
N, K, LDA, LDC
REAL (KIND=nag_wp)
ALPHA, BETA
COMPLEX (KIND=nag_wp)
A(LDA,*), C(LDC,*)
CHARACTER(1)
UPLO, TRANS
The routine may be called by its BLAS name
zherk
.
3 Description
None.
4 References
None.
5 Parameters
1: UPLO – CHARACTER(1)
Input
On entry
: specifies whether the upper or lower triangular part of
C
is stored.
UPLO
=
'U'
The upper triangular part of
C
is stored.
UPLO
=
'L'
The lower triangular part of
C
is stored.
Constraint
:
UPLO
=
'U'
or
'L'
.
2: TRANS – CHARACTER(1)
Input
On entry
: specifies the operation to be performed.
TRANS
=
'N'
C
←
α
A
A
H
+
β
C
.
TRANS
=
'C'
C
←
α
A
H
A
+
β
C
.
Constraint
:
TRANS
=
'N'
or
'C'
.
3: N – INTEGER
Input
On entry
:
n
, the order of the matrix
C
; the number of rows of
A
if
TRANS
=
'N'
, or the number of columns of
A
if
TRANS
=
'T'
or
'C'
.
Constraint
:
N
≥
0
.
4: K – INTEGER
Input
On entry
:
k
, the number of columns of
A
if
TRANS
=
'N'
, or the number of rows of
A
if
TRANS
=
'T'
or
'C'
.
Constraint
:
K
≥
0
.
5: ALPHA – REAL (KIND=nag_wp)
Input
On entry
: the scalar
α
.
6: A(
LDA
,
*
) – COMPLEX (KIND=nag_wp) array
Input
Note:
the second dimension of the array
A
must be at least
max
1
,
K
if
TRANS
=
'N'
and at least
max
1
,
N
if
TRANS
=
'T'
or
'C'
.
On entry
: the matrix
A
;
A
is
n
by
k
if
TRANS
=
'N'
, or
k
by
n
if
TRANS
=
'T'
or
'C'
.
7: LDA – INTEGER
Input
On entry
: the first dimension of the array
A
as declared in the (sub)program from which F06ZPF (ZHERK) is called.
Constraints
:
if
TRANS
=
'N'
,
LDA
≥
max
1
,
N
;
if
TRANS
=
'T'
or
'C'
,
LDA
≥
max
1
,
K
.
8: BETA – REAL (KIND=nag_wp)
Input
On entry
: the scalar
β
.
9: C(
LDC
,
*
) – COMPLEX (KIND=nag_wp) array
Input/Output
Note:
the second dimension of the array
C
must be at least
max
1
,
N
.
On entry
: the
n
by
n
Hermitian matrix
C
.
If
UPLO
=
'U'
, the upper triangular part of
C
must be stored and the elements of the array below the diagonal are not referenced.
If
UPLO
=
'L'
, the lower triangular part of
C
must be stored and the elements of the array above the diagonal are not referenced.
On exit
: the updated matrix
C
. The imaginary parts of the diagonal elements are set to zero.
10: LDC – INTEGER
Input
On entry
: the first dimension of the array
C
as declared in the (sub)program from which F06ZPF (ZHERK) is called.
Constraint
:
LDC
≥
max
1
,
N
.
6 Error Indicators and Warnings
None.
7 Accuracy
Not applicable.
8 Further Comments
None.
9 Example
None.
F06ZPF (ZHERK) (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual
© The Numerical Algorithms Group Ltd, Oxford, UK. 2012