cherk.f man page

cherk.f

Synopsis

Functions/Subroutines

subroutine cherk (UPLO, TRANS, N, K, ALPHA, A, LDA, BETA, C, LDC)
CHERK

Function/Subroutine Documentation

subroutine cherk (character UPLO, character TRANS, integer N, integer K, real ALPHA, complex, dimension(lda,*) A, integer LDA, real BETA, complex, dimension(ldc,*) C, integer LDC)

CHERK

Purpose:

 CHERK  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 REAL
           On entry, ALPHA specifies the scalar alpha.

A

          A is COMPLEX array, 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 REAL
           On entry, BETA specifies the scalar beta.

C

          C is COMPLEX array, 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:

December 2016

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 REAL( C(J,J) ) when BETA = 1.
     Ed Anderson, Cray Research Inc.

Definition at line 175 of file cherk.f.

Author

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Referenced By

The man page cherk(3) is an alias of cherk.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK