LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ cunmql()

subroutine cunmql ( character  SIDE,
character  TRANS,
integer  M,
integer  N,
integer  K,
complex, dimension( lda, * )  A,
integer  LDA,
complex, dimension( * )  TAU,
complex, dimension( ldc, * )  C,
integer  LDC,
complex, dimension( * )  WORK,
integer  LWORK,
integer  INFO 
)

CUNMQL

Download CUNMQL + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 CUNMQL 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 defined as the product of k
 elementary reflectors

       Q = H(k) . . . H(2) H(1)

 as returned by CGEQLF. Q is of order M if SIDE = 'L' and of order N
 if SIDE = 'R'.
Parameters
[in]SIDE
          SIDE is CHARACTER*1
          = 'L': apply Q or Q**H from the Left;
          = 'R': apply Q or Q**H from the Right.
[in]TRANS
          TRANS is CHARACTER*1
          = 'N':  No transpose, apply Q;
          = 'C':  Conjugate transpose, apply Q**H.
[in]M
          M is INTEGER
          The number of rows of the matrix C. M >= 0.
[in]N
          N is INTEGER
          The number of columns of the matrix C. N >= 0.
[in]K
          K is INTEGER
          The number of elementary reflectors whose product defines
          the matrix Q.
          If SIDE = 'L', M >= K >= 0;
          if SIDE = 'R', N >= K >= 0.
[in]A
          A is 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
          CGEQLF in the last k columns of its array argument A.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A.
          If SIDE = 'L', LDA >= max(1,M);
          if SIDE = 'R', LDA >= max(1,N).
[in]TAU
          TAU is COMPLEX array, dimension (K)
          TAU(i) must contain the scalar factor of the elementary
          reflector H(i), as returned by CGEQLF.
[in,out]C
          C is COMPLEX 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.
[in]LDC
          LDC is INTEGER
          The leading dimension of the array C. LDC >= max(1,M).
[out]WORK
          WORK is COMPLEX array, dimension (MAX(1,LWORK))
          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]LWORK
          LWORK is INTEGER
          The dimension of the array WORK.
          If SIDE = 'L', LWORK >= max(1,N);
          if SIDE = 'R', LWORK >= max(1,M).
          For good performance, LWORK should generally be larger.

          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.
[out]INFO
          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 166 of file cunmql.f.

168 *
169 * -- LAPACK computational routine --
170 * -- LAPACK is a software package provided by Univ. of Tennessee, --
171 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
172 *
173 * .. Scalar Arguments ..
174  CHARACTER SIDE, TRANS
175  INTEGER INFO, K, LDA, LDC, LWORK, M, N
176 * ..
177 * .. Array Arguments ..
178  COMPLEX A( LDA, * ), C( LDC, * ), TAU( * ),
179  $ WORK( * )
180 * ..
181 *
182 * =====================================================================
183 *
184 * .. Parameters ..
185  INTEGER NBMAX, LDT, TSIZE
186  parameter( nbmax = 64, ldt = nbmax+1,
187  $ tsize = ldt*nbmax )
188 * ..
189 * .. Local Scalars ..
190  LOGICAL LEFT, LQUERY, NOTRAN
191  INTEGER I, I1, I2, I3, IB, IINFO, IWT, LDWORK, LWKOPT,
192  $ MI, NB, NBMIN, NI, NQ, NW
193 * ..
194 * .. External Functions ..
195  LOGICAL LSAME
196  INTEGER ILAENV
197  EXTERNAL lsame, ilaenv
198 * ..
199 * .. External Subroutines ..
200  EXTERNAL clarfb, clarft, cunm2l, xerbla
201 * ..
202 * .. Intrinsic Functions ..
203  INTRINSIC max, min
204 * ..
205 * .. Executable Statements ..
206 *
207 * Test the input arguments
208 *
209  info = 0
210  left = lsame( side, 'L' )
211  notran = lsame( trans, 'N' )
212  lquery = ( lwork.EQ.-1 )
213 *
214 * NQ is the order of Q and NW is the minimum dimension of WORK
215 *
216  IF( left ) THEN
217  nq = m
218  nw = max( 1, n )
219  ELSE
220  nq = n
221  nw = max( 1, m )
222  END IF
223  IF( .NOT.left .AND. .NOT.lsame( side, 'R' ) ) THEN
224  info = -1
225  ELSE IF( .NOT.notran .AND. .NOT.lsame( trans, 'C' ) ) THEN
226  info = -2
227  ELSE IF( m.LT.0 ) THEN
228  info = -3
229  ELSE IF( n.LT.0 ) THEN
230  info = -4
231  ELSE IF( k.LT.0 .OR. k.GT.nq ) THEN
232  info = -5
233  ELSE IF( lda.LT.max( 1, nq ) ) THEN
234  info = -7
235  ELSE IF( ldc.LT.max( 1, m ) ) THEN
236  info = -10
237  ELSE IF( lwork.LT.nw .AND. .NOT.lquery ) THEN
238  info = -12
239  END IF
240 *
241  IF( info.EQ.0 ) THEN
242 *
243 * Compute the workspace requirements
244 *
245  IF( m.EQ.0 .OR. n.EQ.0 ) THEN
246  lwkopt = 1
247  ELSE
248  nb = min( nbmax, ilaenv( 1, 'CUNMQL', side // trans, m, n,
249  $ k, -1 ) )
250  lwkopt = nw*nb + tsize
251  END IF
252  work( 1 ) = lwkopt
253  END IF
254 *
255  IF( info.NE.0 ) THEN
256  CALL xerbla( 'CUNMQL', -info )
257  RETURN
258  ELSE IF( lquery ) THEN
259  RETURN
260  END IF
261 *
262 * Quick return if possible
263 *
264  IF( m.EQ.0 .OR. n.EQ.0 ) THEN
265  RETURN
266  END IF
267 *
268 * Determine the block size
269 *
270  nbmin = 2
271  ldwork = nw
272  IF( nb.GT.1 .AND. nb.LT.k ) THEN
273  IF( lwork.LT.lwkopt ) THEN
274  nb = (lwork-tsize) / ldwork
275  nbmin = max( 2, ilaenv( 2, 'CUNMQL', side // trans, m, n, k,
276  $ -1 ) )
277  END IF
278  END IF
279 *
280  IF( nb.LT.nbmin .OR. nb.GE.k ) THEN
281 *
282 * Use unblocked code
283 *
284  CALL cunm2l( side, trans, m, n, k, a, lda, tau, c, ldc, work,
285  $ iinfo )
286  ELSE
287 *
288 * Use blocked code
289 *
290  iwt = 1 + nw*nb
291  IF( ( left .AND. notran ) .OR.
292  $ ( .NOT.left .AND. .NOT.notran ) ) THEN
293  i1 = 1
294  i2 = k
295  i3 = nb
296  ELSE
297  i1 = ( ( k-1 ) / nb )*nb + 1
298  i2 = 1
299  i3 = -nb
300  END IF
301 *
302  IF( left ) THEN
303  ni = n
304  ELSE
305  mi = m
306  END IF
307 *
308  DO 10 i = i1, i2, i3
309  ib = min( nb, k-i+1 )
310 *
311 * Form the triangular factor of the block reflector
312 * H = H(i+ib-1) . . . H(i+1) H(i)
313 *
314  CALL clarft( 'Backward', 'Columnwise', nq-k+i+ib-1, ib,
315  $ a( 1, i ), lda, tau( i ), work( iwt ), ldt )
316  IF( left ) THEN
317 *
318 * H or H**H is applied to C(1:m-k+i+ib-1,1:n)
319 *
320  mi = m - k + i + ib - 1
321  ELSE
322 *
323 * H or H**H is applied to C(1:m,1:n-k+i+ib-1)
324 *
325  ni = n - k + i + ib - 1
326  END IF
327 *
328 * Apply H or H**H
329 *
330  CALL clarfb( side, trans, 'Backward', 'Columnwise', mi, ni,
331  $ ib, a( 1, i ), lda, work( iwt ), ldt, c, ldc,
332  $ work, ldwork )
333  10 CONTINUE
334  END IF
335  work( 1 ) = lwkopt
336  RETURN
337 *
338 * End of CUNMQL
339 *
integer function ilaenv(ISPEC, NAME, OPTS, N1, N2, N3, N4)
ILAENV
Definition: ilaenv.f:162
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
subroutine clarfb(SIDE, TRANS, DIRECT, STOREV, M, N, K, V, LDV, T, LDT, C, LDC, WORK, LDWORK)
CLARFB applies a block reflector or its conjugate-transpose to a general rectangular matrix.
Definition: clarfb.f:197
subroutine clarft(DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT)
CLARFT forms the triangular factor T of a block reflector H = I - vtvH
Definition: clarft.f:163
subroutine cunm2l(SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, INFO)
CUNM2L multiplies a general matrix by the unitary matrix from a QL factorization determined by cgeqlf...
Definition: cunm2l.f:159
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