dsymm

DSYMM(1)                         BLAS routine                         DSYMM(1)



NAME
       DSYMM - performs one of the matrix-matrix operations   C := alpha*A*B +
       beta*C,

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

           DOUBLE                                                   PRECISION
                                                                    ALPHA,BETA

           INTEGER                                                  LDA,LDB,LDC,M,N

           CHARACTER                                                SIDE,UPLO

           DOUBLE                                                   PRECISION
                                                                    A(LDA,*),B(LDB,*),C(LDC,*)

PURPOSE
       DSYMM  performs one of the matrix-matrix operations

       or

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

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


ARGUMENTS
       SIDE   - CHARACTER*1.
              On entry,  SIDE  specifies whether  the  symmetric 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  symmetric  matrix   A  is  to  be
              referenced as follows:

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

              UPLO = 'L' or 'l'   Only the lower triangular part of the
              symmetric 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  - DOUBLE PRECISION.
              On entry, ALPHA specifies the scalar alpha.  Unchanged on exit.

       A      - DOUBLE PRECISION 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  symmetric 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  symmetric 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  symmetric 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  symmetric 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
              symmetric 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  symmetric matrix and the
              strictly upper triangular part of  A  is not referenced.
              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      - DOUBLE PRECISION 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   - DOUBLE PRECISION.
              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      - DOUBLE PRECISION 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.

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.




BLAS routine                     November 2008                        DSYMM(1)