zlaset.f

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*> \brief \b ZLASET initializes the off-diagonal elements and the diagonal elements of a matrix to given values.
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download ZLASET + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zlaset.f">
*> [TXT]</a>
*> \endhtmlonly
*
*  Definition:
*  ===========
*
*       SUBROUTINE ZLASET( UPLO, M, N, ALPHA, BETA, A, LDA )
*
*       .. Scalar Arguments ..
*       CHARACTER          UPLO
*       INTEGER            LDA, M, N
*       COMPLEX*16         ALPHA, BETA
*       ..
*       .. Array Arguments ..
*       COMPLEX*16         A( LDA, * )
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> ZLASET initializes a 2-D array A to BETA on the diagonal and
*> ALPHA on the offdiagonals.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] UPLO
*> \verbatim
*>          UPLO is CHARACTER*1
*>          Specifies the part of the matrix A to be set.
*>          = 'U':      Upper triangular part is set. The lower triangle
*>                      is unchanged.
*>          = 'L':      Lower triangular part is set. The upper triangle
*>                      is unchanged.
*>          Otherwise:  All of the matrix A is set.
*> \endverbatim
*>
*> \param[in] M
*> \verbatim
*>          M is INTEGER
*>          On entry, M specifies the number of rows of A.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>          On entry, N specifies the number of columns of A.
*> \endverbatim
*>
*> \param[in] ALPHA
*> \verbatim
*>          ALPHA is COMPLEX*16
*>          All the offdiagonal array elements are set to ALPHA.
*> \endverbatim
*>
*> \param[in] BETA
*> \verbatim
*>          BETA is COMPLEX*16
*>          All the diagonal array elements are set to BETA.
*> \endverbatim
*>
*> \param[out] A
*> \verbatim
*>          A is COMPLEX*16 array, dimension (LDA,N)
*>          On entry, the m by n matrix A.
*>          On exit, A(i,j) = ALPHA, 1 <= i <= m, 1 <= j <= n, i.ne.j;
*>                   A(i,i) = BETA , 1 <= i <= min(m,n)
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*>          LDA is INTEGER
*>          The leading dimension of the array A.  LDA >= max(1,M).
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup laset
*
*  =====================================================================
      SUBROUTINE zlaset( UPLO, M, N, ALPHA, BETA, A, LDA )
*
*  -- LAPACK auxiliary routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      CHARACTER          UPLO
      INTEGER            LDA, M, N
      COMPLEX*16         ALPHA, BETA
*     ..
*     .. Array Arguments ..
      COMPLEX*16         A( LDA, * )
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      INTEGER            I, J
*     ..
*     .. External Functions ..
      LOGICAL            LSAME
      EXTERNAL           lsame
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          min
*     ..
*     .. Executable Statements ..
*
      IF( lsame( uplo, 'U' ) ) THEN
*
*        Set the diagonal to BETA and the strictly upper triangular
*        part of the array to ALPHA.
*
         DO 20 j = 2, n
            DO 10 i = 1, min( j-1, m )
               a( i, j ) = alpha
   10       CONTINUE
   20    CONTINUE
         DO 30 i = 1, min( n, m )
            a( i, i ) = beta
   30    CONTINUE
*
      ELSE IF( lsame( uplo, 'L' ) ) THEN
*
*        Set the diagonal to BETA and the strictly lower triangular
*        part of the array to ALPHA.
*
         DO 50 j = 1, min( m, n )
            DO 40 i = j + 1, m
               a( i, j ) = alpha
   40       CONTINUE
   50    CONTINUE
         DO 60 i = 1, min( n, m )
            a( i, i ) = beta
   60    CONTINUE
*
      ELSE
*
*        Set the array to BETA on the diagonal and ALPHA on the
*        offdiagonal.
*
         DO 80 j = 1, n
            DO 70 i = 1, m
               a( i, j ) = alpha
   70       CONTINUE
   80    CONTINUE
         DO 90 i = 1, min( m, n )
            a( i, i ) = beta
   90    CONTINUE
      END IF
*
      RETURN
*
*     End of ZLASET
*
      END