# zherk.f man page

zherk.f —

## Synopsis

### Functions/Subroutines

subroutinezherk(UPLO, TRANS, N, K, ALPHA, A, LDA, BETA, C, LDC)ZHERK

## Function/Subroutine Documentation

### subroutine zherk (characterUPLO, characterTRANS, integerN, integerK, double precisionALPHA, complex*16, dimension(lda,*)A, integerLDA, double precisionBETA, complex*16, dimension(ldc,*)C, integerLDC)

**ZHERK Purpose:**

```
ZHERK performs one of the hermitian rank k operations
C := alpha*A*A**H + beta*C,
or
C := alpha*A**H*A + beta*C,
where alpha and beta are real scalars, C is an n by n hermitian
matrix and A is an n by k matrix in the first case and a k by n
matrix in the second case.
```

**Parameters:**

*UPLO*

```
UPLO is CHARACTER*1
On entry, UPLO specifies whether the upper or lower
triangular part of the array C is to be referenced as
follows:
UPLO = 'U' or 'u' Only the upper triangular part of C
is to be referenced.
UPLO = 'L' or 'l' Only the lower triangular part of C
is to be referenced.
```

*TRANS*

```
TRANS is CHARACTER*1
On entry, TRANS specifies the operation to be performed as
follows:
TRANS = 'N' or 'n' C := alpha*A*A**H + beta*C.
TRANS = 'C' or 'c' C := alpha*A**H*A + beta*C.
```

*N*

```
N is INTEGER
On entry, N specifies the order of the matrix C. N must be
at least zero.
```

*K*

```
K is INTEGER
On entry with TRANS = 'N' or 'n', K specifies the number
of columns of the matrix A, and on entry with
TRANS = 'C' or 'c', K specifies the number of rows of the
matrix A. K must be at least zero.
```

*ALPHA*

```
ALPHA is DOUBLE PRECISION .
On entry, ALPHA specifies the scalar alpha.
```

*A*

```
A is COMPLEX*16 array of DIMENSION ( LDA, ka ), where ka is
k when TRANS = 'N' or 'n', and is n otherwise.
Before entry with TRANS = 'N' or 'n', the leading n by k
part of the array A must contain the matrix A, otherwise
the leading k by n part of the array A must contain the
matrix A.
```

*LDA*

```
LDA is INTEGER
On entry, LDA specifies the first dimension of A as declared
in the calling (sub) program. When TRANS = 'N' or 'n'
then LDA must be at least max( 1, n ), otherwise LDA must
be at least max( 1, k ).
```

*BETA*

```
BETA is DOUBLE PRECISION.
On entry, BETA specifies the scalar beta.
```

*C*

```
C is COMPLEX*16 array of DIMENSION ( LDC, n ).
Before entry with UPLO = 'U' or 'u', the leading n by n
upper triangular part of the array C must contain the upper
triangular part of the hermitian matrix and the strictly
lower triangular part of C is not referenced. On exit, the
upper triangular part of the array C is overwritten by the
upper triangular part of the updated matrix.
Before entry with UPLO = 'L' or 'l', the leading n by n
lower triangular part of the array C must contain the lower
triangular part of the hermitian matrix and the strictly
upper triangular part of C is not referenced. On exit, the
lower triangular part of the array C is overwritten by the
lower triangular part of the updated matrix.
Note that the imaginary parts of the diagonal elements need
not be set, they are assumed to be zero, and on exit they
are set to zero.
```

*LDC*

```
LDC is INTEGER
On entry, LDC specifies the first dimension of C as declared
in the calling (sub) program. LDC must be at least
max( 1, n ).
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

November 2011

**Further Details:**

```
Level 3 Blas routine.
-- Written on 8-February-1989.
Jack Dongarra, Argonne National Laboratory.
Iain Duff, AERE Harwell.
Jeremy Du Croz, Numerical Algorithms Group Ltd.
Sven Hammarling, Numerical Algorithms Group Ltd.
-- Modified 8-Nov-93 to set C(J,J) to DBLE( C(J,J) ) when BETA = 1.
Ed Anderson, Cray Research Inc.
```

Definition at line 174 of file zherk.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

zherk(3) is an alias of zherk.f(3).