cunm2r.f

          SUBROUTINE CUNM2R( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
         $                   WORK, INFO )
    *
    *  -- LAPACK routine (version 3.1) --
    *     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
    *     November 2006
    *
    *     .. Scalar Arguments ..
          CHARACTER          SIDE, TRANS
          INTEGER            INFO, K, LDA, LDC, M, N
    *     ..
    *     .. Array Arguments ..
          COMPLEX            A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
    *     ..
    *
    *  Purpose
    *  =======
    *
    *  CUNM2R overwrites the general complex m-by-n matrix C with
    *
    *        Q * C  if SIDE = 'L' and TRANS = 'N', or
    *
    *        Q'* C  if SIDE = 'L' and TRANS = 'C', or
    *
    *        C * Q  if SIDE = 'R' and TRANS = 'N', or
    *
    *        C * Q' if SIDE = 'R' and TRANS = 'C',
    *
    *  where Q is a complex unitary matrix defined as the product of k
    *  elementary reflectors
    *
    *        Q = H(1) H(2) . . . H(k)
    *
    *  as returned by CGEQRF. Q is of order m if SIDE = 'L' and of order n
    *  if SIDE = 'R'.
    *
    *  Arguments
    *  =========
    *
    *  SIDE    (input) CHARACTER*1
    *          = 'L': apply Q or Q' from the Left
    *          = 'R': apply Q or Q' from the Right
    *
    *  TRANS   (input) CHARACTER*1
    *          = 'N': apply Q  (No transpose)
    *          = 'C': apply Q' (Conjugate transpose)
    *
    *  M       (input) INTEGER
    *          The number of rows of the matrix C. M >= 0.
    *
    *  N       (input) INTEGER
    *          The number of columns of the matrix C. N >= 0.
    *
    *  K       (input) INTEGER
    *          The number of elementary reflectors whose product defines
    *          the matrix Q.
    *          If SIDE = 'L', M >= K >= 0;
    *          if SIDE = 'R', N >= K >= 0.
    *
    *  A       (input) COMPLEX array, dimension (LDA,K)
    *          The i-th column must contain the vector which defines the
    *          elementary reflector H(i), for i = 1,2,...,k, as returned by
    *          CGEQRF in the first k columns of its array argument A.
    *          A is modified by the routine but restored on exit.
    *
    *  LDA     (input) INTEGER
    *          The leading dimension of the array A.
    *          If SIDE = 'L', LDA >= max(1,M);
    *          if SIDE = 'R', LDA >= max(1,N).
    *
    *  TAU     (input) COMPLEX array, dimension (K)
    *          TAU(i) must contain the scalar factor of the elementary
    *          reflector H(i), as returned by CGEQRF.
    *
    *  C       (input/output) COMPLEX array, dimension (LDC,N)
    *          On entry, the m-by-n matrix C.
    *          On exit, C is overwritten by Q*C or Q'*C or C*Q' or C*Q.
    *
    *  LDC     (input) INTEGER
    *          The leading dimension of the array C. LDC >= max(1,M).
    *
    *  WORK    (workspace) COMPLEX array, dimension
    *                                   (N) if SIDE = 'L',
    *                                   (M) if SIDE = 'R'
    *
    *  INFO    (output) INTEGER
    *          = 0: successful exit
    *          < 0: if INFO = -i, the i-th argument had an illegal value
    *
    *  =====================================================================
    *
    *     .. Parameters ..
          COMPLEX            ONE
          PARAMETER          ( ONE = ( 1.0E+0, 0.0E+0 ) )
    *     ..
    *     .. Local Scalars ..
          LOGICAL            LEFT, NOTRAN
          INTEGER            I, I1, I2, I3, IC, JC, MI, NI, NQ
          COMPLEX            AII, TAUI
    *     ..
    *     .. External Functions ..
          LOGICAL            LSAME
          EXTERNAL           LSAME
    *     ..
    *     .. External Subroutines ..
          EXTERNAL           CLARF, XERBLA
    *     ..
    *     .. Intrinsic Functions ..
          INTRINSIC          CONJG, MAX
    *     ..
    *     .. Executable Statements ..
    *
    *     Test the input arguments
    *
          INFO = 0
          LEFT = LSAME( SIDE, 'L' )
          NOTRAN = LSAME( TRANS, 'N' )
    *
    *     NQ is the order of Q
    *
          IF( LEFT ) THEN
             NQ = M
          ELSE
             NQ = N
          END IF
          IF( .NOT.LEFT .AND. .NOT.LSAME( SIDE, 'R' ) ) THEN
             INFO = -1
          ELSE IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS, 'C' ) ) THEN
             INFO = -2
          ELSE IF( M.LT.0 ) THEN
             INFO = -3
          ELSE IF( N.LT.0 ) THEN
             INFO = -4
          ELSE IF( K.LT.0 .OR. K.GT.NQ ) THEN
             INFO = -5
          ELSE IF( LDA.LT.MAX( 1, NQ ) ) THEN
             INFO = -7
          ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
             INFO = -10
          END IF
          IF( INFO.NE.0 ) THEN
             CALL XERBLA( 'CUNM2R', -INFO )
             RETURN
          END IF
    *
    *     Quick return if possible
    *
          IF( M.EQ.0 .OR. N.EQ.0 .OR. K.EQ.0 )
         $   RETURN
    *
          IF( ( LEFT .AND. .NOT.NOTRAN .OR. .NOT.LEFT .AND. NOTRAN ) ) THEN
             I1 = 1
             I2 = K
             I3 = 1
          ELSE
             I1 = K
             I2 = 1
             I3 = -1
          END IF
    *
          IF( LEFT ) THEN
             NI = N
             JC = 1
          ELSE
             MI = M
             IC = 1
          END IF
    *
          DO 10 I = I1, I2, I3
             IF( LEFT ) THEN
    *
    *           H(i) or H(i)' is applied to C(i:m,1:n)
    *
                MI = M - I + 1
                IC = I
             ELSE
    *
    *           H(i) or H(i)' is applied to C(1:m,i:n)
    *
                NI = N - I + 1
                JC = I
             END IF
    *
    *        Apply H(i) or H(i)'
    *
             IF( NOTRAN ) THEN
                TAUI = TAU( I )
             ELSE
                TAUI = CONJG( TAU( I ) )
             END IF
             AII = A( I, I )
             A( I, I ) = ONE
             CALL CLARF( SIDE, MI, NI, A( I, I ), 1, TAUI, C( IC, JC ), LDC,
         $               WORK )
             A( I, I ) = AII
       10 CONTINUE
          RETURN
    *
    *     End of CUNM2R
    *
          END