LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ cunmtr()

subroutine cunmtr ( character  side,
character  uplo,
character  trans,
integer  m,
integer  n,
complex, dimension( lda, * )  a,
integer  lda,
complex, dimension( * )  tau,
complex, dimension( ldc, * )  c,
integer  ldc,
complex, dimension( * )  work,
integer  lwork,
integer  info 
)

CUNMTR

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

Purpose:
 CUNMTR 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
 nq-1 elementary reflectors, as returned by CHETRD:

 if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);

 if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
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]UPLO
          UPLO is CHARACTER*1
          = 'U': Upper triangle of A contains elementary reflectors
                 from CHETRD;
          = 'L': Lower triangle of A contains elementary reflectors
                 from CHETRD.
[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]A
          A is COMPLEX array, dimension
                               (LDA,M) if SIDE = 'L'
                               (LDA,N) if SIDE = 'R'
          The vectors which define the elementary reflectors, as
          returned by CHETRD.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A.
          LDA >= max(1,M) if SIDE = 'L'; LDA >= max(1,N) if SIDE = 'R'.
[in]TAU
          TAU is COMPLEX 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 CHETRD.
[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 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.
[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 170 of file cunmtr.f.

172*
173* -- LAPACK computational routine --
174* -- LAPACK is a software package provided by Univ. of Tennessee, --
175* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
176*
177* .. Scalar Arguments ..
178 CHARACTER SIDE, TRANS, UPLO
179 INTEGER INFO, LDA, LDC, LWORK, M, N
180* ..
181* .. Array Arguments ..
182 COMPLEX A( LDA, * ), C( LDC, * ), TAU( * ),
183 $ WORK( * )
184* ..
185*
186* =====================================================================
187*
188* .. Local Scalars ..
189 LOGICAL LEFT, LQUERY, UPPER
190 INTEGER I1, I2, IINFO, LWKOPT, MI, NB, NI, NQ, NW
191* ..
192* .. External Functions ..
193 LOGICAL LSAME
194 INTEGER ILAENV
195 REAL SROUNDUP_LWORK
196 EXTERNAL ilaenv, lsame, sroundup_lwork
197* ..
198* .. External Subroutines ..
199 EXTERNAL cunmql, cunmqr, xerbla
200* ..
201* .. Intrinsic Functions ..
202 INTRINSIC max
203* ..
204* .. Executable Statements ..
205*
206* Test the input arguments
207*
208 info = 0
209 left = lsame( side, 'L' )
210 upper = lsame( uplo, 'U' )
211 lquery = ( lwork.EQ.-1 )
212*
213* NQ is the order of Q and NW is the minimum dimension of WORK
214*
215 IF( left ) THEN
216 nq = m
217 nw = max( 1, n )
218 ELSE
219 nq = n
220 nw = max( 1, m )
221 END IF
222 IF( .NOT.left .AND. .NOT.lsame( side, 'R' ) ) THEN
223 info = -1
224 ELSE IF( .NOT.upper .AND. .NOT.lsame( uplo, 'L' ) ) THEN
225 info = -2
226 ELSE IF( .NOT.lsame( trans, 'N' ) .AND. .NOT.lsame( trans, 'C' ) )
227 $ THEN
228 info = -3
229 ELSE IF( m.LT.0 ) THEN
230 info = -4
231 ELSE IF( n.LT.0 ) 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 IF( upper ) THEN
243 IF( left ) THEN
244 nb = ilaenv( 1, 'CUNMQL', side // trans, m-1, n, m-1,
245 $ -1 )
246 ELSE
247 nb = ilaenv( 1, 'CUNMQL', side // trans, m, n-1, n-1,
248 $ -1 )
249 END IF
250 ELSE
251 IF( left ) THEN
252 nb = ilaenv( 1, 'CUNMQR', side // trans, m-1, n, m-1,
253 $ -1 )
254 ELSE
255 nb = ilaenv( 1, 'CUNMQR', side // trans, m, n-1, n-1,
256 $ -1 )
257 END IF
258 END IF
259 lwkopt = nw*nb
260 work( 1 ) = sroundup_lwork(lwkopt)
261 END IF
262*
263 IF( info.NE.0 ) THEN
264 CALL xerbla( 'CUNMTR', -info )
265 RETURN
266 ELSE IF( lquery ) THEN
267 RETURN
268 END IF
269*
270* Quick return if possible
271*
272 IF( m.EQ.0 .OR. n.EQ.0 .OR. nq.EQ.1 ) THEN
273 work( 1 ) = 1
274 RETURN
275 END IF
276*
277 IF( left ) THEN
278 mi = m - 1
279 ni = n
280 ELSE
281 mi = m
282 ni = n - 1
283 END IF
284*
285 IF( upper ) THEN
286*
287* Q was determined by a call to CHETRD with UPLO = 'U'
288*
289 CALL cunmql( side, trans, mi, ni, nq-1, a( 1, 2 ), lda, tau, c,
290 $ ldc, work, lwork, iinfo )
291 ELSE
292*
293* Q was determined by a call to CHETRD with UPLO = 'L'
294*
295 IF( left ) THEN
296 i1 = 2
297 i2 = 1
298 ELSE
299 i1 = 1
300 i2 = 2
301 END IF
302 CALL cunmqr( side, trans, mi, ni, nq-1, a( 2, 1 ), lda, tau,
303 $ c( i1, i2 ), ldc, work, lwork, iinfo )
304 END IF
305 work( 1 ) = sroundup_lwork(lwkopt)
306 RETURN
307*
308* End of CUNMTR
309*
subroutine xerbla(srname, info)
Definition cblat2.f:3285
integer function ilaenv(ispec, name, opts, n1, n2, n3, n4)
ILAENV
Definition ilaenv.f:162
logical function lsame(ca, cb)
LSAME
Definition lsame.f:48
real function sroundup_lwork(lwork)
SROUNDUP_LWORK
subroutine cunmql(side, trans, m, n, k, a, lda, tau, c, ldc, work, lwork, info)
CUNMQL
Definition cunmql.f:168
subroutine cunmqr(side, trans, m, n, k, a, lda, tau, c, ldc, work, lwork, info)
CUNMQR
Definition cunmqr.f:168
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