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      SUBROUTINE ZSYRKF ( UPLO, TRANS, N, K, ALPHA, A, LDA,
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     $                   BETA, C, LDC )
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*     .. Scalar Arguments ..
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      CHARACTER*1        UPLO, TRANS
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      INTEGER            N, K, LDA, LDC
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      COMPLEX*16         ALPHA, BETA
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*     .. Array Arguments ..
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      COMPLEX*16         A( LDA, * ), C( LDC, * )
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*     ..
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*
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*  Purpose
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*  =======
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*
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*  ZSYRK  performs one of the symmetric rank k operations
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*
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*     C := alpha*A*A' + beta*C,
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*
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*  or
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*
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*     C := alpha*A'*A + beta*C,
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*
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*  where  alpha and beta  are scalars,  C is an  n by n symmetric matrix
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*  and  A  is an  n by k  matrix in the first case and a  k by n  matrix
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*  in the second case.
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*
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*  Parameters
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*  ==========
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*
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*  UPLO   - CHARACTER*1.
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*           On  entry,   UPLO  specifies  whether  the  upper  or  lower
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*           triangular  part  of the  array  C  is to be  referenced  as
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*           follows:
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*
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*              UPLO = 'U' or 'u'   Only the  upper triangular part of  C
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*                                  is to be referenced.
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*
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*              UPLO = 'L' or 'l'   Only the  lower triangular part of  C
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*                                  is to be referenced.
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*
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*           Unchanged on exit.
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*
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*  TRANS  - CHARACTER*1.
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*           On entry,  TRANS  specifies the operation to be performed as
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*           follows:
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*
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*              TRANS = 'N' or 'n'   C := alpha*A*A' + beta*C.
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*
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*              TRANS = 'T' or 't'   C := alpha*A'*A + beta*C.
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*
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*           Unchanged on exit.
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*
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*  N      - INTEGER.
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*           On entry,  N specifies the order of the matrix C.  N must be
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*           at least zero.
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*           Unchanged on exit.
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*
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*  K      - INTEGER.
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*           On entry with  TRANS = 'N' or 'n',  K  specifies  the number
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*           of  columns   of  the   matrix   A,   and  on   entry   with
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*           TRANS = 'T' or 't',  K  specifies  the number of rows of the
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*           matrix A.  K must be at least zero.
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*           Unchanged on exit.
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*
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*  ALPHA  - COMPLEX*16      .
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*           On entry, ALPHA specifies the scalar alpha.
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*           Unchanged on exit.
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*
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*  A      - COMPLEX*16       array of DIMENSION ( LDA, ka ), where ka is
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*           k  when  TRANS = 'N' or 'n',  and is  n  otherwise.
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*           Before entry with  TRANS = 'N' or 'n',  the  leading  n by k
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*           part of the array  A  must contain the matrix  A,  otherwise
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*           the leading  k by n  part of the array  A  must contain  the
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*           matrix A.
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*           Unchanged on exit.
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*
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*  LDA    - INTEGER.
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*           On entry, LDA specifies the first dimension of A as declared
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*           in  the  calling  (sub)  program.   When  TRANS = 'N' or 'n'
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*           then  LDA must be at least  max( 1, n ), otherwise  LDA must
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*           be at least  max( 1, k ).
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*           Unchanged on exit.
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*
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*  BETA   - COMPLEX*16      .
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*           On entry, BETA specifies the scalar beta.
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*           Unchanged on exit.
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*
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*  C      - COMPLEX*16       array of DIMENSION ( LDC, n ).
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*           Before entry  with  UPLO = 'U' or 'u',  the leading  n by n
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*           upper triangular part of the array C must contain the upper
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*           triangular part  of the  symmetric matrix  and the strictly
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*           lower triangular part of C is not referenced.  On exit, the
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*           upper triangular part of the array  C is overwritten by the
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*           upper triangular part of the updated matrix.
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*           Before entry  with  UPLO = 'L' or 'l',  the leading  n by n
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*           lower triangular part of the array C must contain the lower
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*           triangular part  of the  symmetric matrix  and the strictly
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*           upper triangular part of C is not referenced.  On exit, the
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*           lower triangular part of the array  C is overwritten by the
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*           lower triangular part of the updated matrix.
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*
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*  LDC    - INTEGER.
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*           On entry, LDC specifies the first dimension of C as declared
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*           in  the  calling  (sub)  program.   LDC  must  be  at  least
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*           max( 1, n ).
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*           Unchanged on exit.
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*
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*
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*  Level 3 Blas routine.
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*
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*  -- Written on 8-February-1989.
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*     Jack Dongarra, Argonne National Laboratory.
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*     Iain Duff, AERE Harwell.
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*     Jeremy Du Croz, Numerical Algorithms Group Ltd.
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*     Sven Hammarling, Numerical Algorithms Group Ltd.
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*
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*
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*     .. External Functions ..
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      LOGICAL            LSAME
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      EXTERNAL           LSAME
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*     .. External Subroutines ..
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      EXTERNAL           XERBLA
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*     .. Intrinsic Functions ..
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      INTRINSIC          MAX
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*     .. Local Scalars ..
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      LOGICAL            UPPER
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      INTEGER            I, INFO, J, L, NROWA
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      COMPLEX*16         TEMP
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*     .. Parameters ..
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      COMPLEX*16         ONE
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      PARAMETER        ( ONE  = ( 1.0D+0, 0.0D+0 ) )
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      COMPLEX*16         ZERO
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      PARAMETER        ( ZERO = ( 0.0D+0, 0.0D+0 ) )
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*     ..
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*     .. Executable Statements ..
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*
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*     Test the input parameters.
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*
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      IF( LSAME( TRANS, 'N' ) )THEN
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         NROWA = N
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      ELSE
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         NROWA = K
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      END IF
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      UPPER = LSAME( UPLO, 'U' )
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*
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      INFO = 0
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      IF(      ( .NOT.UPPER               ).AND.
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     $         ( .NOT.LSAME( UPLO , 'L' ) )      )THEN
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         INFO = 1
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      ELSE IF( ( .NOT.LSAME( TRANS, 'N' ) ).AND.
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     $         ( .NOT.LSAME( TRANS, 'T' ) )      )THEN
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         INFO = 2
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      ELSE IF( N  .LT.0               )THEN
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         INFO = 3
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      ELSE IF( K  .LT.0               )THEN
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         INFO = 4
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      ELSE IF( LDA.LT.MAX( 1, NROWA ) )THEN
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         INFO = 7
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      ELSE IF( LDC.LT.MAX( 1, N     ) )THEN
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         INFO = 10
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      END IF
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      IF( INFO.NE.0 )THEN
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         CALL XERBLA( 'ZSYRK ', INFO )
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         RETURN
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      END IF
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*
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*     Quick return if possible.
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*
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      IF( ( N.EQ.0 ).OR.
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     $    ( ( ( ALPHA.EQ.ZERO ).OR.( K.EQ.0 ) ).AND.( BETA.EQ.ONE ) ) )
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     $   RETURN
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*
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*     And when  alpha.eq.zero.
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*
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      IF( ALPHA.EQ.ZERO )THEN
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         IF( UPPER )THEN
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            IF( BETA.EQ.ZERO )THEN
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               DO 20, J = 1, N
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                  DO 10, I = 1, J
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                     C( I, J ) = ZERO
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   10             CONTINUE
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   20          CONTINUE
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            ELSE
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               DO 40, J = 1, N
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                  DO 30, I = 1, J
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                     C( I, J ) = BETA*C( I, J )
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   30             CONTINUE
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   40          CONTINUE
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            END IF
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         ELSE
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            IF( BETA.EQ.ZERO )THEN
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               DO 60, J = 1, N
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                  DO 50, I = J, N
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                     C( I, J ) = ZERO
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   50             CONTINUE
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   60          CONTINUE
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            ELSE
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               DO 80, J = 1, N
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                  DO 70, I = J, N
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                     C( I, J ) = BETA*C( I, J )
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   70             CONTINUE
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   80          CONTINUE
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            END IF
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         END IF
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         RETURN
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      END IF
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*
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*     Start the operations.
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*
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      IF( LSAME( TRANS, 'N' ) )THEN
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*
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*        Form  C := alpha*A*A' + beta*C.
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*
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         IF( UPPER )THEN
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            DO 130, J = 1, N
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               IF( BETA.EQ.ZERO )THEN
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                  DO 90, I = 1, J
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                     C( I, J ) = ZERO
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   90             CONTINUE
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               ELSE IF( BETA.NE.ONE )THEN
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                  DO 100, I = 1, J
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                     C( I, J ) = BETA*C( I, J )
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  100             CONTINUE
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               END IF
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               DO 120, L = 1, K
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                  IF( A( J, L ).NE.ZERO )THEN
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                     TEMP = ALPHA*A( J, L )
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                     DO 110, I = 1, J
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                        C( I, J ) = C( I, J ) + TEMP*A( I, L )
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  110                CONTINUE
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                  END IF
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  120          CONTINUE
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  130       CONTINUE
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         ELSE
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            DO 180, J = 1, N
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               IF( BETA.EQ.ZERO )THEN
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                  DO 140, I = J, N
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                     C( I, J ) = ZERO
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  140             CONTINUE
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               ELSE IF( BETA.NE.ONE )THEN
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                  DO 150, I = J, N
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                     C( I, J ) = BETA*C( I, J )
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  150             CONTINUE
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               END IF
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               DO 170, L = 1, K
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                  IF( A( J, L ).NE.ZERO )THEN
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                     TEMP      = ALPHA*A( J, L )
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                     DO 160, I = J, N
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                        C( I, J ) = C( I, J ) + TEMP*A( I, L )
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  160                CONTINUE
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                  END IF
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  170          CONTINUE
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  180       CONTINUE
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         END IF
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      ELSE
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*
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*        Form  C := alpha*A'*A + beta*C.
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*
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         IF( UPPER )THEN
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            DO 210, J = 1, N
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               DO 200, I = 1, J
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                  TEMP = ZERO
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                  DO 190, L = 1, K
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                     TEMP = TEMP + A( L, I )*A( L, J )
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  190             CONTINUE
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                  IF( BETA.EQ.ZERO )THEN
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                     C( I, J ) = ALPHA*TEMP
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                  ELSE
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                     C( I, J ) = ALPHA*TEMP + BETA*C( I, J )
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                  END IF
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  200          CONTINUE
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  210       CONTINUE
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         ELSE
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            DO 240, J = 1, N
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               DO 230, I = J, N
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                  TEMP = ZERO
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                  DO 220, L = 1, K
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                     TEMP = TEMP + A( L, I )*A( L, J )
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  220             CONTINUE
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                  IF( BETA.EQ.ZERO )THEN
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                     C( I, J ) = ALPHA*TEMP
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                  ELSE
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                     C( I, J ) = ALPHA*TEMP + BETA*C( I, J )
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                  END IF
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  230          CONTINUE
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  240       CONTINUE
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         END IF
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      END IF
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*
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      RETURN
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*
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*     End of ZSYRK .
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*
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      END