zlarcm.f

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*> \brief \b ZLARCM copies all or part of a real two-dimensional array to a complex array.
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
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*
*  Definition:
*  ===========
*
*       SUBROUTINE ZLARCM( M, N, A, LDA, B, LDB, C, LDC, RWORK )
*
*       .. Scalar Arguments ..
*       INTEGER            LDA, LDB, LDC, M, N
*       ..
*       .. Array Arguments ..
*       DOUBLE PRECISION   A( LDA, * ), RWORK( * )
*       COMPLEX*16         B( LDB, * ), C( LDC, * )
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> ZLARCM performs a very simple matrix-matrix multiplication:
*>          C := A * B,
*> where A is M by M and real; B is M by N and complex;
*> C is M by N and complex.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] M
*> \verbatim
*>          M is INTEGER
*>          The number of rows of the matrix A and of the matrix C.
*>          M >= 0.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>          The number of columns and rows of the matrix B and
*>          the number of columns of the matrix C.
*>          N >= 0.
*> \endverbatim
*>
*> \param[in] A
*> \verbatim
*>          A is DOUBLE PRECISION array, dimension (LDA, M)
*>          On entry, A contains the M by M matrix A.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*>          LDA is INTEGER
*>          The leading dimension of the array A. LDA >=max(1,M).
*> \endverbatim
*>
*> \param[in] B
*> \verbatim
*>          B is COMPLEX*16 array, dimension (LDB, N)
*>          On entry, B contains the M by N matrix B.
*> \endverbatim
*>
*> \param[in] LDB
*> \verbatim
*>          LDB is INTEGER
*>          The leading dimension of the array B. LDB >=max(1,M).
*> \endverbatim
*>
*> \param[out] C
*> \verbatim
*>          C is COMPLEX*16 array, dimension (LDC, N)
*>          On exit, C contains the M by N matrix C.
*> \endverbatim
*>
*> \param[in] LDC
*> \verbatim
*>          LDC is INTEGER
*>          The leading dimension of the array C. LDC >=max(1,M).
*> \endverbatim
*>
*> \param[out] RWORK
*> \verbatim
*>          RWORK is DOUBLE PRECISION array, dimension (2*M*N)
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup larcm
*
*  =====================================================================
      SUBROUTINE zlarcm( M, N, A, LDA, B, LDB, C, LDC, RWORK )
*
*  -- 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 ..
      INTEGER            LDA, LDB, LDC, M, N
*     ..
*     .. Array Arguments ..
      DOUBLE PRECISION   A( LDA, * ), RWORK( * )
      COMPLEX*16         B( LDB, * ), C( LDC, * )
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION   ONE, ZERO
      parameter( one = 1.0d0, zero = 0.0d0 )
*     ..
*     .. Local Scalars ..
      INTEGER            I, J, L
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          dble, dcmplx, dimag
*     ..
*     .. External Subroutines ..
      EXTERNAL           dgemm
*     ..
*     .. Executable Statements ..
*
*     Quick return if possible.
*
      IF( ( m.EQ.0 ) .OR. ( n.EQ.0 ) )
     $   RETURN
*
      DO 20 j = 1, n
         DO 10 i = 1, m
            rwork( ( j-1 )*m+i ) = dble( b( i, j ) )
   10    CONTINUE
   20 CONTINUE
*
      l = m*n + 1
      CALL dgemm( 'N', 'N', m, n, m, one, a, lda, rwork, m, zero,
     $            rwork( l ), m )
      DO 40 j = 1, n
         DO 30 i = 1, m
            c( i, j ) = rwork( l+( j-1 )*m+i-1 )
   30    CONTINUE
   40 CONTINUE
*
      DO 60 j = 1, n
         DO 50 i = 1, m
            rwork( ( j-1 )*m+i ) = dimag( b( i, j ) )
   50    CONTINUE
   60 CONTINUE
      CALL dgemm( 'N', 'N', m, n, m, one, a, lda, rwork, m, zero,
     $            rwork( l ), m )
      DO 80 j = 1, n
         DO 70 i = 1, m
            c( i, j ) = dcmplx( dble( c( i, j ) ),
     $                  rwork( l+( j-1 )*m+i-1 ) )
   70    CONTINUE
   80 CONTINUE
*
      RETURN
*
*     End of ZLARCM
*
      END