Homepage > Man Pages > Category > Subroutines
Homepage > Man Pages > Name > Z

# zhemm

## man page of zhemm

### zhemm: perform one of the matrix-matrix operations C := alpha*A*B + beta*C,

```NAME
ZHEMM  - perform one of the matrix-matrix operations   C := alpha*A*B +
beta*C,

SYNOPSIS
SUBROUTINE ZHEMM ( SIDE, UPLO, M, N, ALPHA, A, LDA, B,  LDB,  BETA,  C,
LDC )

CHARACTER*1  SIDE, UPLO

INTEGER      M, N, LDA, LDB, LDC

COMPLEX*16   ALPHA, BETA

COMPLEX*16   A( LDA, * ), B( LDB, * ), C( LDC, * )

PURPOSE
ZHEMM  performs one of the matrix-matrix operations

or

C := alpha*B*A + beta*C,

where alpha and beta are scalars, A is an hermitian matrix and  B and C
are m by n matrices.

PARAMETERS
SIDE   - CHARACTER*1.
On entry,  SIDE  specifies whether   the   hermitian  matrix   A
appears on the  left or right  in the  operation as follows:

SIDE = 'L' or 'l'   C := alpha*A*B + beta*C,

SIDE = 'R' or 'r'   C := alpha*B*A + beta*C,

Unchanged on exit.

UPLO   - CHARACTER*1.
On   entry,    UPLO   specifies   whether  the  upper  or  lower
triangular  part  of  the  hermitian  matrix    A   is   to   be
referenced as follows:

UPLO  =  'U'  or  'u'    Only  the  upper triangular part of the
hermitian matrix is to be referenced.

UPLO = 'L' or 'l'    Only  the  lower  triangular  part  of  the
hermitian matrix is to be referenced.

Unchanged on exit.

M      - INTEGER.
On  entry,  M  specifies the number of rows of the matrix  C.  M
must be at least zero.  Unchanged on exit.

N      - INTEGER.
On entry, N specifies the number of columns of the matrix C.   N
must be at least zero.  Unchanged on exit.

ALPHA  - COMPLEX*16      .
On entry, ALPHA specifies the scalar alpha.  Unchanged on exit.

A      - COMPLEX*16       array of DIMENSION ( LDA, ka ), where ka is
m   when   SIDE = 'L' or 'l'  and is n  otherwise.  Before entry
with  SIDE = 'L' or 'l',  the  m by m   part  of  the  array   A
must  contain the  hermitian matrix,  such that when  UPLO = 'U'
or 'u', the leading m by m upper triangular part of the array  A
must  contain the upper triangular part of the  hermitian matrix
and  the   strictly   lower  triangular  part  of   A   is   not
referenced,   and  when   UPLO = 'L' or 'l', the leading  m by m
lower triangular part  of  the   array   A  must   contain   the
lower   triangular  part   of  the   hermitian  matrix  and  the
strictly upper triangular part of  A  is not referenced.  Before
entry   with  SIDE = 'R' or 'r',  the  n by n  part of the array
A  must contain the  hermitian matrix,  such that when   UPLO  =
'U'  or  'u',  the  leading  n by n upper triangular part of the
array   A   must  contain  the  upper  triangular  part  of  the
hermitian  matrix and the  strictly  lower triangular part of  A
is not referenced,  and when  UPLO = 'L' or 'l', the leading   n
by n  lower triangular part  of the  array  A must  contain  the
lower  triangular  part   of  the   hermitian  matrix  and   the
strictly  upper  triangular part of  A  is not referenced.  Note
that the imaginary parts  of the diagonal elements need  not  be
set, they are assumed to be zero.  Unchanged on exit.

LDA    - INTEGER.
On  entry, LDA specifies the first dimension of A as declared in
the  calling (sub) program. When  SIDE = 'L' or  'l'   then  LDA
must  be  at least  max( 1, m ), otherwise  LDA must be at least
max( 1, n ).  Unchanged on exit.

B      - COMPLEX*16       array of DIMENSION ( LDB, n ).
Before entry, the leading  m by n part of  the  array   B   must
contain the matrix B.  Unchanged on exit.

LDB    - INTEGER.
On  entry, LDB specifies the first dimension of B as declared in
the  calling  (sub)  program.   LDB  must  be  at  least max( 1,
m ).  Unchanged on exit.

BETA   - COMPLEX*16      .
On  entry,   BETA   specifies  the scalar  beta.  When  BETA  is
supplied as zero then C need not be set on input.  Unchanged  on
exit.

C      - COMPLEX*16       array of DIMENSION ( LDC, n ).
Before  entry,  the  leading   m by n  part of the array  C must
contain the matrix  C,  except when  beta   is  zero,  in  which
case  C  need  not  be  set on entry.  On exit, the array  C  is
overwritten by the  m by n updated matrix.

LDC    - INTEGER.
On entry, LDC specifies the first dimension of C as declared  in
the  calling  (sub)  program.   LDC  must  be  at  least max( 1,
m ).  Unchanged on exit.

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.

ZHEMM(3)
```