LAPACK 3.11.0 LAPACK: Linear Algebra PACKage
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## ◆ cunmrq()

 subroutine cunmrq ( 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 )

CUNMRQ

Purpose:
``` CUNMRQ 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(1)**H H(2)**H . . . H(k)**H

as returned by CGERQF. 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,M) if SIDE = 'L', (LDA,N) if SIDE = 'R' The i-th row must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by CGERQF in the last k rows of its array argument A.``` [in] LDA ``` LDA is INTEGER The leading dimension of the array A. LDA >= max(1,K).``` [in] TAU ``` TAU is COMPLEX array, dimension (K) TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CGERQF.``` [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```

Definition at line 166 of file cunmrq.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 CHARACTER TRANST
192 INTEGER I, I1, I2, I3, IB, IINFO, IWT, LDWORK, LWKOPT,
193 \$ MI, NB, NBMIN, NI, NQ, NW
194* ..
195* .. External Functions ..
196 LOGICAL LSAME
197 INTEGER ILAENV
198 EXTERNAL lsame, ilaenv
199* ..
200* .. External Subroutines ..
201 EXTERNAL clarfb, clarft, cunmr2, xerbla
202* ..
203* .. Intrinsic Functions ..
204 INTRINSIC max, min
205* ..
206* .. Executable Statements ..
207*
208* Test the input arguments
209*
210 info = 0
211 left = lsame( side, 'L' )
212 notran = lsame( trans, 'N' )
213 lquery = ( lwork.EQ.-1 )
214*
215* NQ is the order of Q and NW is the minimum dimension of WORK
216*
217 IF( left ) THEN
218 nq = m
219 nw = max( 1, n )
220 ELSE
221 nq = n
222 nw = max( 1, m )
223 END IF
224 IF( .NOT.left .AND. .NOT.lsame( side, 'R' ) ) THEN
225 info = -1
226 ELSE IF( .NOT.notran .AND. .NOT.lsame( trans, 'C' ) ) THEN
227 info = -2
228 ELSE IF( m.LT.0 ) THEN
229 info = -3
230 ELSE IF( n.LT.0 ) THEN
231 info = -4
232 ELSE IF( k.LT.0 .OR. k.GT.nq ) THEN
233 info = -5
234 ELSE IF( lda.LT.max( 1, k ) ) THEN
235 info = -7
236 ELSE IF( ldc.LT.max( 1, m ) ) THEN
237 info = -10
238 ELSE IF( lwork.LT.nw .AND. .NOT.lquery ) THEN
239 info = -12
240 END IF
241*
242 IF( info.EQ.0 ) THEN
243*
244* Compute the workspace requirements
245*
246 IF( m.EQ.0 .OR. n.EQ.0 ) THEN
247 lwkopt = 1
248 ELSE
249 nb = min( nbmax, ilaenv( 1, 'CUNMRQ', side // trans, m, n,
250 \$ k, -1 ) )
251 lwkopt = nw*nb + tsize
252 END IF
253 work( 1 ) = lwkopt
254 END IF
255*
256 IF( info.NE.0 ) THEN
257 CALL xerbla( 'CUNMRQ', -info )
258 RETURN
259 ELSE IF( lquery ) THEN
260 RETURN
261 END IF
262*
263* Quick return if possible
264*
265 IF( m.EQ.0 .OR. n.EQ.0 ) THEN
266 RETURN
267 END IF
268*
269 nbmin = 2
270 ldwork = nw
271 IF( nb.GT.1 .AND. nb.LT.k ) THEN
272 IF( lwork.LT.lwkopt ) THEN
273 nb = (lwork-tsize) / ldwork
274 nbmin = max( 2, ilaenv( 2, 'CUNMRQ', side // trans, m, n, k,
275 \$ -1 ) )
276 END IF
277 END IF
278*
279 IF( nb.LT.nbmin .OR. nb.GE.k ) THEN
280*
281* Use unblocked code
282*
283 CALL cunmr2( side, trans, m, n, k, a, lda, tau, c, ldc, work,
284 \$ iinfo )
285 ELSE
286*
287* Use blocked code
288*
289 iwt = 1 + nw*nb
290 IF( ( left .AND. .NOT.notran ) .OR.
291 \$ ( .NOT.left .AND. notran ) ) THEN
292 i1 = 1
293 i2 = k
294 i3 = nb
295 ELSE
296 i1 = ( ( k-1 ) / nb )*nb + 1
297 i2 = 1
298 i3 = -nb
299 END IF
300*
301 IF( left ) THEN
302 ni = n
303 ELSE
304 mi = m
305 END IF
306*
307 IF( notran ) THEN
308 transt = 'C'
309 ELSE
310 transt = 'N'
311 END IF
312*
313 DO 10 i = i1, i2, i3
314 ib = min( nb, k-i+1 )
315*
316* Form the triangular factor of the block reflector
317* H = H(i+ib-1) . . . H(i+1) H(i)
318*
319 CALL clarft( 'Backward', 'Rowwise', nq-k+i+ib-1, ib,
320 \$ a( i, 1 ), lda, tau( i ), work( iwt ), ldt )
321 IF( left ) THEN
322*
323* H or H**H is applied to C(1:m-k+i+ib-1,1:n)
324*
325 mi = m - k + i + ib - 1
326 ELSE
327*
328* H or H**H is applied to C(1:m,1:n-k+i+ib-1)
329*
330 ni = n - k + i + ib - 1
331 END IF
332*
333* Apply H or H**H
334*
335 CALL clarfb( side, transt, 'Backward', 'Rowwise', mi, ni,
336 \$ ib, a( i, 1 ), lda, work( iwt ), ldt, c, ldc,
337 \$ work, ldwork )
338 10 CONTINUE
339 END IF
340 work( 1 ) = lwkopt
341 RETURN
342*
343* End of CUNMRQ
344*
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 cunmr2(SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, INFO)
CUNMR2 multiplies a general matrix by the unitary matrix from a RQ factorization determined by cgerqf...
Definition: cunmr2.f:159
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