LAPACK 3.3.1 Linear Algebra PACKage

# cunmhr.f

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```00001       SUBROUTINE CUNMHR( SIDE, TRANS, M, N, ILO, IHI, A, LDA, TAU, C,
00002      \$                   LDC, WORK, LWORK, INFO )
00003 *
00004 *  -- LAPACK routine (version 3.2) --
00005 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00006 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00007 *     November 2006
00008 *
00009 *     .. Scalar Arguments ..
00010       CHARACTER          SIDE, TRANS
00011       INTEGER            IHI, ILO, INFO, LDA, LDC, LWORK, M, N
00012 *     ..
00013 *     .. Array Arguments ..
00014       COMPLEX            A( LDA, * ), C( LDC, * ), TAU( * ),
00015      \$                   WORK( * )
00016 *     ..
00017 *
00018 *  Purpose
00019 *  =======
00020 *
00021 *  CUNMHR overwrites the general complex M-by-N matrix C with
00022 *
00023 *                  SIDE = 'L'     SIDE = 'R'
00024 *  TRANS = 'N':      Q * C          C * Q
00025 *  TRANS = 'C':      Q**H * C       C * Q**H
00026 *
00027 *  where Q is a complex unitary matrix of order nq, with nq = m if
00028 *  SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
00029 *  IHI-ILO elementary reflectors, as returned by CGEHRD:
00030 *
00031 *  Q = H(ilo) H(ilo+1) . . . H(ihi-1).
00032 *
00033 *  Arguments
00034 *  =========
00035 *
00036 *  SIDE    (input) CHARACTER*1
00037 *          = 'L': apply Q or Q**H from the Left;
00038 *          = 'R': apply Q or Q**H from the Right.
00039 *
00040 *  TRANS   (input) CHARACTER*1
00041 *          = 'N': apply Q  (No transpose)
00042 *          = 'C': apply Q**H (Conjugate transpose)
00043 *
00044 *  M       (input) INTEGER
00045 *          The number of rows of the matrix C. M >= 0.
00046 *
00047 *  N       (input) INTEGER
00048 *          The number of columns of the matrix C. N >= 0.
00049 *
00050 *  ILO     (input) INTEGER
00051 *  IHI     (input) INTEGER
00052 *          ILO and IHI must have the same values as in the previous call
00053 *          of CGEHRD. Q is equal to the unit matrix except in the
00054 *          submatrix Q(ilo+1:ihi,ilo+1:ihi).
00055 *          If SIDE = 'L', then 1 <= ILO <= IHI <= M, if M > 0, and
00056 *          ILO = 1 and IHI = 0, if M = 0;
00057 *          if SIDE = 'R', then 1 <= ILO <= IHI <= N, if N > 0, and
00058 *          ILO = 1 and IHI = 0, if N = 0.
00059 *
00060 *  A       (input) COMPLEX array, dimension
00061 *                               (LDA,M) if SIDE = 'L'
00062 *                               (LDA,N) if SIDE = 'R'
00063 *          The vectors which define the elementary reflectors, as
00064 *          returned by CGEHRD.
00065 *
00066 *  LDA     (input) INTEGER
00067 *          The leading dimension of the array A.
00068 *          LDA >= max(1,M) if SIDE = 'L'; LDA >= max(1,N) if SIDE = 'R'.
00069 *
00070 *  TAU     (input) COMPLEX array, dimension
00071 *                               (M-1) if SIDE = 'L'
00072 *                               (N-1) if SIDE = 'R'
00073 *          TAU(i) must contain the scalar factor of the elementary
00074 *          reflector H(i), as returned by CGEHRD.
00075 *
00076 *  C       (input/output) COMPLEX array, dimension (LDC,N)
00077 *          On entry, the M-by-N matrix C.
00078 *          On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
00079 *
00080 *  LDC     (input) INTEGER
00081 *          The leading dimension of the array C. LDC >= max(1,M).
00082 *
00083 *  WORK    (workspace/output) COMPLEX array, dimension (MAX(1,LWORK))
00084 *          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
00085 *
00086 *  LWORK   (input) INTEGER
00087 *          The dimension of the array WORK.
00088 *          If SIDE = 'L', LWORK >= max(1,N);
00089 *          if SIDE = 'R', LWORK >= max(1,M).
00090 *          For optimum performance LWORK >= N*NB if SIDE = 'L', and
00091 *          LWORK >= M*NB if SIDE = 'R', where NB is the optimal
00092 *          blocksize.
00093 *
00094 *          If LWORK = -1, then a workspace query is assumed; the routine
00095 *          only calculates the optimal size of the WORK array, returns
00096 *          this value as the first entry of the WORK array, and no error
00097 *          message related to LWORK is issued by XERBLA.
00098 *
00099 *  INFO    (output) INTEGER
00100 *          = 0:  successful exit
00101 *          < 0:  if INFO = -i, the i-th argument had an illegal value
00102 *
00103 *  =====================================================================
00104 *
00105 *     .. Local Scalars ..
00106       LOGICAL            LEFT, LQUERY
00107       INTEGER            I1, I2, IINFO, LWKOPT, MI, NB, NH, NI, NQ, NW
00108 *     ..
00109 *     .. External Functions ..
00110       LOGICAL            LSAME
00111       INTEGER            ILAENV
00112       EXTERNAL           ILAENV, LSAME
00113 *     ..
00114 *     .. External Subroutines ..
00115       EXTERNAL           CUNMQR, XERBLA
00116 *     ..
00117 *     .. Intrinsic Functions ..
00118       INTRINSIC          MAX, MIN
00119 *     ..
00120 *     .. Executable Statements ..
00121 *
00122 *     Test the input arguments
00123 *
00124       INFO = 0
00125       NH = IHI - ILO
00126       LEFT = LSAME( SIDE, 'L' )
00127       LQUERY = ( LWORK.EQ.-1 )
00128 *
00129 *     NQ is the order of Q and NW is the minimum dimension of WORK
00130 *
00131       IF( LEFT ) THEN
00132          NQ = M
00133          NW = N
00134       ELSE
00135          NQ = N
00136          NW = M
00137       END IF
00138       IF( .NOT.LEFT .AND. .NOT.LSAME( SIDE, 'R' ) ) THEN
00139          INFO = -1
00140       ELSE IF( .NOT.LSAME( TRANS, 'N' ) .AND. .NOT.LSAME( TRANS, 'C' ) )
00141      \$          THEN
00142          INFO = -2
00143       ELSE IF( M.LT.0 ) THEN
00144          INFO = -3
00145       ELSE IF( N.LT.0 ) THEN
00146          INFO = -4
00147       ELSE IF( ILO.LT.1 .OR. ILO.GT.MAX( 1, NQ ) ) THEN
00148          INFO = -5
00149       ELSE IF( IHI.LT.MIN( ILO, NQ ) .OR. IHI.GT.NQ ) THEN
00150          INFO = -6
00151       ELSE IF( LDA.LT.MAX( 1, NQ ) ) THEN
00152          INFO = -8
00153       ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
00154          INFO = -11
00155       ELSE IF( LWORK.LT.MAX( 1, NW ) .AND. .NOT.LQUERY ) THEN
00156          INFO = -13
00157       END IF
00158 *
00159       IF( INFO.EQ.0 ) THEN
00160          IF( LEFT ) THEN
00161             NB = ILAENV( 1, 'CUNMQR', SIDE // TRANS, NH, N, NH, -1 )
00162          ELSE
00163             NB = ILAENV( 1, 'CUNMQR', SIDE // TRANS, M, NH, NH, -1 )
00164          END IF
00165          LWKOPT = MAX( 1, NW )*NB
00166          WORK( 1 ) = LWKOPT
00167       END IF
00168 *
00169       IF( INFO.NE.0 ) THEN
00170          CALL XERBLA( 'CUNMHR', -INFO )
00171          RETURN
00172       ELSE IF( LQUERY ) THEN
00173          RETURN
00174       END IF
00175 *
00176 *     Quick return if possible
00177 *
00178       IF( M.EQ.0 .OR. N.EQ.0 .OR. NH.EQ.0 ) THEN
00179          WORK( 1 ) = 1
00180          RETURN
00181       END IF
00182 *
00183       IF( LEFT ) THEN
00184          MI = NH
00185          NI = N
00186          I1 = ILO + 1
00187          I2 = 1
00188       ELSE
00189          MI = M
00190          NI = NH
00191          I1 = 1
00192          I2 = ILO + 1
00193       END IF
00194 *
00195       CALL CUNMQR( SIDE, TRANS, MI, NI, NH, A( ILO+1, ILO ), LDA,
00196      \$             TAU( ILO ), C( I1, I2 ), LDC, WORK, LWORK, IINFO )
00197 *
00198       WORK( 1 ) = LWKOPT
00199       RETURN
00200 *
00201 *     End of CUNMHR
00202 *
00203       END
```