clacrm.f

Go to the documentation of this file.

*> \brief \b CLACRM multiplies a complex matrix by a square real matrix.
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> Download CLACRM + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/clacrm.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/clacrm.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/clacrm.f">
*> [TXT]</a>
*
*  Definition:
*  ===========
*
*       SUBROUTINE CLACRM( M, N, A, LDA, B, LDB, C, LDC, RWORK )
*
*       .. Scalar Arguments ..
*       INTEGER            LDA, LDB, LDC, M, N
*       ..
*       .. Array Arguments ..
*       REAL               B( LDB, * ), RWORK( * )
*       COMPLEX            A( LDA, * ), C( LDC, * )
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> CLACRM performs a very simple matrix-matrix multiplication:
*>          C := A * B,
*> where A is M by N and complex; B is N by N and real;
*> 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 COMPLEX array, dimension (LDA, N)
*>          On entry, A contains the M by N 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 REAL array, dimension (LDB, N)
*>          On entry, B contains the N by N matrix B.
*> \endverbatim
*>
*> \param[in] LDB
*> \verbatim
*>          LDB is INTEGER
*>          The leading dimension of the array B. LDB >=max(1,N).
*> \endverbatim
*>
*> \param[out] C
*> \verbatim
*>          C is COMPLEX 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,N).
*> \endverbatim
*>
*> \param[out] RWORK
*> \verbatim
*>          RWORK is REAL 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 lacrm
*
*  =====================================================================
      SUBROUTINE clacrm( 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 ..
      REAL               B( LDB, * ), RWORK( * )
      COMPLEX            A( LDA, * ), C( LDC, * )
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               ONE, ZERO
      parameter( one = 1.0e0, zero = 0.0e0 )
*     ..
*     .. Local Scalars ..
      INTEGER            I, J, L
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          aimag, cmplx, real
*     ..
*     .. External Subroutines ..
      EXTERNAL           sgemm
*     ..
*     .. 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 ) = real( a( i, j ) )
   10    CONTINUE
   20 CONTINUE
*
      l = m*n + 1
      CALL sgemm( 'N', 'N', m, n, n, one, rwork, m, b, ldb, 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 ) = aimag( a( i, j ) )
   50    CONTINUE
   60 CONTINUE
      CALL sgemm( 'N', 'N', m, n, n, one, rwork, m, b, ldb, zero,
     $            rwork( l ), m )
      DO 80 j = 1, n
         DO 70 i = 1, m
            c( i, j ) = cmplx( real( c( i, j ) ),
     $                  rwork( l+( j-1 )*m+i-1 ) )
   70    CONTINUE
   80 CONTINUE
*
      RETURN
*
*     End of CLACRM
*
      END