zunmhr.f

          SUBROUTINE ZUNMHR( SIDE, TRANS, M, N, ILO, IHI, A, LDA, TAU, C,
         $                   LDC, WORK, LWORK, INFO )
    *
    *  -- LAPACK routine (version 3.1) --
    *     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
    *     November 2006
    *
    *     .. Scalar Arguments ..
          CHARACTER          SIDE, TRANS
          INTEGER            IHI, ILO, INFO, LDA, LDC, LWORK, M, N
    *     ..
    *     .. Array Arguments ..
          COMPLEX*16         A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
    *     ..
    *
    *  Purpose
    *  =======
    *
    *  ZUNMHR overwrites the general complex M-by-N matrix C with
    *
    *                  SIDE = 'L'     SIDE = 'R'
    *  TRANS = 'N':      Q * C          C * Q
    *  TRANS = 'C':      Q**H * C       C * Q**H
    *
    *  where Q is a complex unitary matrix of order nq, with nq = m if
    *  SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
    *  IHI-ILO elementary reflectors, as returned by ZGEHRD:
    *
    *  Q = H(ilo) H(ilo+1) . . . H(ihi-1).
    *
    *  Arguments
    *  =========
    *
    *  SIDE    (input) CHARACTER*1
    *          = 'L': apply Q or Q**H from the Left;
    *          = 'R': apply Q or Q**H from the Right.
    *
    *  TRANS   (input) CHARACTER*1
    *          = 'N': apply Q  (No transpose)
    *          = 'C': apply Q**H (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.
    *
    *  ILO     (input) INTEGER
    *  IHI     (input) INTEGER
    *          ILO and IHI must have the same values as in the previous call
    *          of ZGEHRD. Q is equal to the unit matrix except in the
    *          submatrix Q(ilo+1:ihi,ilo+1:ihi).
    *          If SIDE = 'L', then 1 <= ILO <= IHI <= M, if M > 0, and
    *          ILO = 1 and IHI = 0, if M = 0;
    *          if SIDE = 'R', then 1 <= ILO <= IHI <= N, if N > 0, and
    *          ILO = 1 and IHI = 0, if N = 0.
    *
    *  A       (input) COMPLEX*16 array, dimension
    *                               (LDA,M) if SIDE = 'L'
    *                               (LDA,N) if SIDE = 'R'
    *          The vectors which define the elementary reflectors, as
    *          returned by ZGEHRD.
    *
    *  LDA     (input) INTEGER
    *          The leading dimension of the array A.
    *          LDA >= max(1,M) if SIDE = 'L'; LDA >= max(1,N) if SIDE = 'R'.
    *
    *  TAU     (input) COMPLEX*16 array, dimension
    *                               (M-1) if SIDE = 'L'
    *                               (N-1) if SIDE = 'R'
    *          TAU(i) must contain the scalar factor of the elementary
    *          reflector H(i), as returned by ZGEHRD.
    *
    *  C       (input/output) COMPLEX*16 array, dimension (LDC,N)
    *          On entry, the M-by-N matrix C.
    *          On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
    *
    *  LDC     (input) INTEGER
    *          The leading dimension of the array C. LDC >= max(1,M).
    *
    *  WORK    (workspace/output) COMPLEX*16 array, dimension (MAX(1,LWORK))
    *          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
    *
    *  LWORK   (input) INTEGER
    *          The dimension of the array WORK.
    *          If SIDE = 'L', LWORK >= max(1,N);
    *          if SIDE = 'R', LWORK >= max(1,M).
    *          For optimum performance LWORK >= N*NB if SIDE = 'L', and
    *          LWORK >= M*NB if SIDE = 'R', where NB is the optimal
    *          blocksize.
    *
    *          If LWORK = -1, then a workspace query is assumed; the routine
    *          only calculates the optimal size of the WORK array, returns
    *          this value as the first entry of the WORK array, and no error
    *          message related to LWORK is issued by XERBLA.
    *
    *  INFO    (output) INTEGER
    *          = 0:  successful exit
    *          < 0:  if INFO = -i, the i-th argument had an illegal value
    *
    *  =====================================================================
    *
    *     .. Local Scalars ..
          LOGICAL            LEFT, LQUERY
          INTEGER            I1, I2, IINFO, LWKOPT, MI, NB, NH, NI, NQ, NW
    *     ..
    *     .. External Functions ..
          LOGICAL            LSAME
          INTEGER            ILAENV
          EXTERNAL           LSAME, ILAENV
    *     ..
    *     .. External Subroutines ..
          EXTERNAL           XERBLA, ZUNMQR
    *     ..
    *     .. Intrinsic Functions ..
          INTRINSIC          MAX, MIN
    *     ..
    *     .. Executable Statements ..
    *
    *     Test the input arguments
    *
          INFO = 0
          NH = IHI - ILO
          LEFT = LSAME( SIDE, 'L' )
          LQUERY = ( LWORK.EQ.-1 )
    *
    *     NQ is the order of Q and NW is the minimum dimension of WORK
    *
          IF( LEFT ) THEN
             NQ = M
             NW = N
          ELSE
             NQ = N
             NW = M
          END IF
          IF( .NOT.LEFT .AND. .NOT.LSAME( SIDE, 'R' ) ) THEN
             INFO = -1
          ELSE IF( .NOT.LSAME( TRANS, 'N' ) .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( ILO.LT.1 .OR. ILO.GT.MAX( 1, NQ ) ) THEN
             INFO = -5
          ELSE IF( IHI.LT.MIN( ILO, NQ ) .OR. IHI.GT.NQ ) THEN
             INFO = -6
          ELSE IF( LDA.LT.MAX( 1, NQ ) ) THEN
             INFO = -8
          ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
             INFO = -11
          ELSE IF( LWORK.LT.MAX( 1, NW ) .AND. .NOT.LQUERY ) THEN
             INFO = -13
          END IF
    *
          IF( INFO.EQ.0 ) THEN
             IF( LEFT ) THEN
                NB = ILAENV( 1, 'ZUNMQR', SIDE // TRANS, NH, N, NH, -1 )
             ELSE
                NB = ILAENV( 1, 'ZUNMQR', SIDE // TRANS, M, NH, NH, -1 )
             END IF
             LWKOPT = MAX( 1, NW )*NB
             WORK( 1 ) = LWKOPT
          END IF
    *
          IF( INFO.NE.0 ) THEN
             CALL XERBLA( 'ZUNMHR', -INFO )
             RETURN
          ELSE IF( LQUERY ) THEN
             RETURN
          END IF
    *
    *     Quick return if possible
    *
          IF( M.EQ.0 .OR. N.EQ.0 .OR. NH.EQ.0 ) THEN
             WORK( 1 ) = 1
             RETURN
          END IF
    *
          IF( LEFT ) THEN
             MI = NH
             NI = N
             I1 = ILO + 1
             I2 = 1
          ELSE
             MI = M
             NI = NH
             I1 = 1
             I2 = ILO + 1
          END IF
    *
          CALL ZUNMQR( SIDE, TRANS, MI, NI, NH, A( ILO+1, ILO ), LDA,
         $             TAU( ILO ), C( I1, I2 ), LDC, WORK, LWORK, IINFO )
    *
          WORK( 1 ) = LWKOPT
          RETURN
    *
    *     End of ZUNMHR
    *
          END