LAPACK  3.4.1
LAPACK: Linear Algebra PACKage
zunmql.f
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00001 *> \brief \b ZUNMQL
00002 *
00003 *  =========== DOCUMENTATION ===========
00004 *
00005 * Online html documentation available at 
00006 *            http://www.netlib.org/lapack/explore-html/ 
00007 *
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00009 *> Download ZUNMQL + dependencies 
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00015 *> [TXT]</a>
00016 *> \endhtmlonly 
00017 *
00018 *  Definition:
00019 *  ===========
00020 *
00021 *       SUBROUTINE ZUNMQL( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
00022 *                          WORK, LWORK, INFO )
00023 * 
00024 *       .. Scalar Arguments ..
00025 *       CHARACTER          SIDE, TRANS
00026 *       INTEGER            INFO, K, LDA, LDC, LWORK, M, N
00027 *       ..
00028 *       .. Array Arguments ..
00029 *       COMPLEX*16         A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
00030 *       ..
00031 *  
00032 *
00033 *> \par Purpose:
00034 *  =============
00035 *>
00036 *> \verbatim
00037 *>
00038 *> ZUNMQL overwrites the general complex M-by-N matrix C with
00039 *>
00040 *>                 SIDE = 'L'     SIDE = 'R'
00041 *> TRANS = 'N':      Q * C          C * Q
00042 *> TRANS = 'C':      Q**H * C       C * Q**H
00043 *>
00044 *> where Q is a complex unitary matrix defined as the product of k
00045 *> elementary reflectors
00046 *>
00047 *>       Q = H(k) . . . H(2) H(1)
00048 *>
00049 *> as returned by ZGEQLF. Q is of order M if SIDE = 'L' and of order N
00050 *> if SIDE = 'R'.
00051 *> \endverbatim
00052 *
00053 *  Arguments:
00054 *  ==========
00055 *
00056 *> \param[in] SIDE
00057 *> \verbatim
00058 *>          SIDE is CHARACTER*1
00059 *>          = 'L': apply Q or Q**H from the Left;
00060 *>          = 'R': apply Q or Q**H from the Right.
00061 *> \endverbatim
00062 *>
00063 *> \param[in] TRANS
00064 *> \verbatim
00065 *>          TRANS is CHARACTER*1
00066 *>          = 'N':  No transpose, apply Q;
00067 *>          = 'C':  Transpose, apply Q**H.
00068 *> \endverbatim
00069 *>
00070 *> \param[in] M
00071 *> \verbatim
00072 *>          M is INTEGER
00073 *>          The number of rows of the matrix C. M >= 0.
00074 *> \endverbatim
00075 *>
00076 *> \param[in] N
00077 *> \verbatim
00078 *>          N is INTEGER
00079 *>          The number of columns of the matrix C. N >= 0.
00080 *> \endverbatim
00081 *>
00082 *> \param[in] K
00083 *> \verbatim
00084 *>          K is INTEGER
00085 *>          The number of elementary reflectors whose product defines
00086 *>          the matrix Q.
00087 *>          If SIDE = 'L', M >= K >= 0;
00088 *>          if SIDE = 'R', N >= K >= 0.
00089 *> \endverbatim
00090 *>
00091 *> \param[in] A
00092 *> \verbatim
00093 *>          A is COMPLEX*16 array, dimension (LDA,K)
00094 *>          The i-th column must contain the vector which defines the
00095 *>          elementary reflector H(i), for i = 1,2,...,k, as returned by
00096 *>          ZGEQLF in the last k columns of its array argument A.
00097 *> \endverbatim
00098 *>
00099 *> \param[in] LDA
00100 *> \verbatim
00101 *>          LDA is INTEGER
00102 *>          The leading dimension of the array A.
00103 *>          If SIDE = 'L', LDA >= max(1,M);
00104 *>          if SIDE = 'R', LDA >= max(1,N).
00105 *> \endverbatim
00106 *>
00107 *> \param[in] TAU
00108 *> \verbatim
00109 *>          TAU is COMPLEX*16 array, dimension (K)
00110 *>          TAU(i) must contain the scalar factor of the elementary
00111 *>          reflector H(i), as returned by ZGEQLF.
00112 *> \endverbatim
00113 *>
00114 *> \param[in,out] C
00115 *> \verbatim
00116 *>          C is COMPLEX*16 array, dimension (LDC,N)
00117 *>          On entry, the M-by-N matrix C.
00118 *>          On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
00119 *> \endverbatim
00120 *>
00121 *> \param[in] LDC
00122 *> \verbatim
00123 *>          LDC is INTEGER
00124 *>          The leading dimension of the array C. LDC >= max(1,M).
00125 *> \endverbatim
00126 *>
00127 *> \param[out] WORK
00128 *> \verbatim
00129 *>          WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
00130 *>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
00131 *> \endverbatim
00132 *>
00133 *> \param[in] LWORK
00134 *> \verbatim
00135 *>          LWORK is INTEGER
00136 *>          The dimension of the array WORK.
00137 *>          If SIDE = 'L', LWORK >= max(1,N);
00138 *>          if SIDE = 'R', LWORK >= max(1,M).
00139 *>          For optimum performance LWORK >= N*NB if SIDE = 'L', and
00140 *>          LWORK >= M*NB if SIDE = 'R', where NB is the optimal
00141 *>          blocksize.
00142 *>
00143 *>          If LWORK = -1, then a workspace query is assumed; the routine
00144 *>          only calculates the optimal size of the WORK array, returns
00145 *>          this value as the first entry of the WORK array, and no error
00146 *>          message related to LWORK is issued by XERBLA.
00147 *> \endverbatim
00148 *>
00149 *> \param[out] INFO
00150 *> \verbatim
00151 *>          INFO is INTEGER
00152 *>          = 0:  successful exit
00153 *>          < 0:  if INFO = -i, the i-th argument had an illegal value
00154 *> \endverbatim
00155 *
00156 *  Authors:
00157 *  ========
00158 *
00159 *> \author Univ. of Tennessee 
00160 *> \author Univ. of California Berkeley 
00161 *> \author Univ. of Colorado Denver 
00162 *> \author NAG Ltd. 
00163 *
00164 *> \date November 2011
00165 *
00166 *> \ingroup complex16OTHERcomputational
00167 *
00168 *  =====================================================================
00169       SUBROUTINE ZUNMQL( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
00170      $                   WORK, LWORK, INFO )
00171 *
00172 *  -- LAPACK computational routine (version 3.4.0) --
00173 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00174 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00175 *     November 2011
00176 *
00177 *     .. Scalar Arguments ..
00178       CHARACTER          SIDE, TRANS
00179       INTEGER            INFO, K, LDA, LDC, LWORK, M, N
00180 *     ..
00181 *     .. Array Arguments ..
00182       COMPLEX*16         A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
00183 *     ..
00184 *
00185 *  =====================================================================
00186 *
00187 *     .. Parameters ..
00188       INTEGER            NBMAX, LDT
00189       PARAMETER          ( NBMAX = 64, LDT = NBMAX+1 )
00190 *     ..
00191 *     .. Local Scalars ..
00192       LOGICAL            LEFT, LQUERY, NOTRAN
00193       INTEGER            I, I1, I2, I3, IB, IINFO, IWS, LDWORK, LWKOPT,
00194      $                   MI, NB, NBMIN, NI, NQ, NW
00195 *     ..
00196 *     .. Local Arrays ..
00197       COMPLEX*16         T( LDT, NBMAX )
00198 *     ..
00199 *     .. External Functions ..
00200       LOGICAL            LSAME
00201       INTEGER            ILAENV
00202       EXTERNAL           LSAME, ILAENV
00203 *     ..
00204 *     .. External Subroutines ..
00205       EXTERNAL           XERBLA, ZLARFB, ZLARFT, ZUNM2L
00206 *     ..
00207 *     .. Intrinsic Functions ..
00208       INTRINSIC          MAX, MIN
00209 *     ..
00210 *     .. Executable Statements ..
00211 *
00212 *     Test the input arguments
00213 *
00214       INFO = 0
00215       LEFT = LSAME( SIDE, 'L' )
00216       NOTRAN = LSAME( TRANS, 'N' )
00217       LQUERY = ( LWORK.EQ.-1 )
00218 *
00219 *     NQ is the order of Q and NW is the minimum dimension of WORK
00220 *
00221       IF( LEFT ) THEN
00222          NQ = M
00223          NW = MAX( 1, N )
00224       ELSE
00225          NQ = N
00226          NW = MAX( 1, M )
00227       END IF
00228       IF( .NOT.LEFT .AND. .NOT.LSAME( SIDE, 'R' ) ) THEN
00229          INFO = -1
00230       ELSE IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS, 'C' ) ) THEN
00231          INFO = -2
00232       ELSE IF( M.LT.0 ) THEN
00233          INFO = -3
00234       ELSE IF( N.LT.0 ) THEN
00235          INFO = -4
00236       ELSE IF( K.LT.0 .OR. K.GT.NQ ) THEN
00237          INFO = -5
00238       ELSE IF( LDA.LT.MAX( 1, NQ ) ) THEN
00239          INFO = -7
00240       ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
00241          INFO = -10
00242       END IF
00243 *
00244       IF( INFO.EQ.0 ) THEN
00245          IF( M.EQ.0 .OR. N.EQ.0 ) THEN
00246             LWKOPT = 1
00247          ELSE
00248 *
00249 *           Determine the block size.  NB may be at most NBMAX, where
00250 *           NBMAX is used to define the local array T.
00251 *
00252             NB = MIN( NBMAX, ILAENV( 1, 'ZUNMQL', SIDE // TRANS, M, N,
00253      $                               K, -1 ) )
00254             LWKOPT = NW*NB
00255          END IF
00256          WORK( 1 ) = LWKOPT
00257 *
00258          IF( LWORK.LT.NW .AND. .NOT.LQUERY ) THEN
00259             INFO = -12
00260          END IF
00261       END IF
00262 *
00263       IF( INFO.NE.0 ) THEN
00264          CALL XERBLA( 'ZUNMQL', -INFO )
00265          RETURN
00266       ELSE IF( LQUERY ) THEN
00267          RETURN
00268       END IF
00269 *
00270 *     Quick return if possible
00271 *
00272       IF( M.EQ.0 .OR. N.EQ.0 ) THEN
00273          RETURN
00274       END IF
00275 *
00276       NBMIN = 2
00277       LDWORK = NW
00278       IF( NB.GT.1 .AND. NB.LT.K ) THEN
00279          IWS = NW*NB
00280          IF( LWORK.LT.IWS ) THEN
00281             NB = LWORK / LDWORK
00282             NBMIN = MAX( 2, ILAENV( 2, 'ZUNMQL', SIDE // TRANS, M, N, K,
00283      $              -1 ) )
00284          END IF
00285       ELSE
00286          IWS = NW
00287       END IF
00288 *
00289       IF( NB.LT.NBMIN .OR. NB.GE.K ) THEN
00290 *
00291 *        Use unblocked code
00292 *
00293          CALL ZUNM2L( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK,
00294      $                IINFO )
00295       ELSE
00296 *
00297 *        Use blocked code
00298 *
00299          IF( ( LEFT .AND. NOTRAN ) .OR.
00300      $       ( .NOT.LEFT .AND. .NOT.NOTRAN ) ) THEN
00301             I1 = 1
00302             I2 = K
00303             I3 = NB
00304          ELSE
00305             I1 = ( ( K-1 ) / NB )*NB + 1
00306             I2 = 1
00307             I3 = -NB
00308          END IF
00309 *
00310          IF( LEFT ) THEN
00311             NI = N
00312          ELSE
00313             MI = M
00314          END IF
00315 *
00316          DO 10 I = I1, I2, I3
00317             IB = MIN( NB, K-I+1 )
00318 *
00319 *           Form the triangular factor of the block reflector
00320 *           H = H(i+ib-1) . . . H(i+1) H(i)
00321 *
00322             CALL ZLARFT( 'Backward', 'Columnwise', NQ-K+I+IB-1, IB,
00323      $                   A( 1, I ), LDA, TAU( I ), T, LDT )
00324             IF( LEFT ) THEN
00325 *
00326 *              H or H**H is applied to C(1:m-k+i+ib-1,1:n)
00327 *
00328                MI = M - K + I + IB - 1
00329             ELSE
00330 *
00331 *              H or H**H is applied to C(1:m,1:n-k+i+ib-1)
00332 *
00333                NI = N - K + I + IB - 1
00334             END IF
00335 *
00336 *           Apply H or H**H
00337 *
00338             CALL ZLARFB( SIDE, TRANS, 'Backward', 'Columnwise', MI, NI,
00339      $                   IB, A( 1, I ), LDA, T, LDT, C, LDC, WORK,
00340      $                   LDWORK )
00341    10    CONTINUE
00342       END IF
00343       WORK( 1 ) = LWKOPT
00344       RETURN
00345 *
00346 *     End of ZUNMQL
00347 *
00348       END
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