LAPACK  3.6.1 LAPACK: Linear Algebra PACKage
 subroutine sorm2r ( character SIDE, character TRANS, integer M, integer N, integer K, real, dimension( lda, * ) A, integer LDA, real, dimension( * ) TAU, real, dimension( ldc, * ) C, integer LDC, real, dimension( * ) WORK, integer INFO )

SORM2R multiplies a general matrix by the orthogonal matrix from a QR factorization determined by sgeqrf (unblocked algorithm).

Download SORM2R + dependencies [TGZ] [ZIP] [TXT]

Purpose:
``` SORM2R overwrites the general real m by n matrix C with

Q * C  if SIDE = 'L' and TRANS = 'N', or

Q**T* C  if SIDE = 'L' and TRANS = 'T', or

C * Q  if SIDE = 'R' and TRANS = 'N', or

C * Q**T if SIDE = 'R' and TRANS = 'T',

where Q is a real orthogonal matrix defined as the product of k
elementary reflectors

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

as returned by SGEQRF. 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**T from the Left = 'R': apply Q or Q**T from the Right``` [in] TRANS ``` TRANS is CHARACTER*1 = 'N': apply Q (No transpose) = 'T': apply Q**T (Transpose)``` [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 REAL 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 SGEQRF in the first k columns of its array argument A. A is modified by the routine but restored on exit.``` [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 REAL array, dimension (K) TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SGEQRF.``` [in,out] C ``` C is REAL array, dimension (LDC,N) On entry, the m by n matrix C. On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.``` [in] LDC ``` LDC is INTEGER The leading dimension of the array C. LDC >= max(1,M).``` [out] WORK ``` WORK is REAL array, dimension (N) if SIDE = 'L', (M) if SIDE = 'R'``` [out] INFO ``` INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value```
Date
September 2012

Definition at line 161 of file sorm2r.f.

161 *
162 * -- LAPACK computational routine (version 3.4.2) --
163 * -- LAPACK is a software package provided by Univ. of Tennessee, --
164 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
165 * September 2012
166 *
167 * .. Scalar Arguments ..
168  CHARACTER side, trans
169  INTEGER info, k, lda, ldc, m, n
170 * ..
171 * .. Array Arguments ..
172  REAL a( lda, * ), c( ldc, * ), tau( * ), work( * )
173 * ..
174 *
175 * =====================================================================
176 *
177 * .. Parameters ..
178  REAL one
179  parameter ( one = 1.0e+0 )
180 * ..
181 * .. Local Scalars ..
182  LOGICAL left, notran
183  INTEGER i, i1, i2, i3, ic, jc, mi, ni, nq
184  REAL aii
185 * ..
186 * .. External Functions ..
187  LOGICAL lsame
188  EXTERNAL lsame
189 * ..
190 * .. External Subroutines ..
191  EXTERNAL slarf, xerbla
192 * ..
193 * .. Intrinsic Functions ..
194  INTRINSIC max
195 * ..
196 * .. Executable Statements ..
197 *
198 * Test the input arguments
199 *
200  info = 0
201  left = lsame( side, 'L' )
202  notran = lsame( trans, 'N' )
203 *
204 * NQ is the order of Q
205 *
206  IF( left ) THEN
207  nq = m
208  ELSE
209  nq = n
210  END IF
211  IF( .NOT.left .AND. .NOT.lsame( side, 'R' ) ) THEN
212  info = -1
213  ELSE IF( .NOT.notran .AND. .NOT.lsame( trans, 'T' ) ) THEN
214  info = -2
215  ELSE IF( m.LT.0 ) THEN
216  info = -3
217  ELSE IF( n.LT.0 ) THEN
218  info = -4
219  ELSE IF( k.LT.0 .OR. k.GT.nq ) THEN
220  info = -5
221  ELSE IF( lda.LT.max( 1, nq ) ) THEN
222  info = -7
223  ELSE IF( ldc.LT.max( 1, m ) ) THEN
224  info = -10
225  END IF
226  IF( info.NE.0 ) THEN
227  CALL xerbla( 'SORM2R', -info )
228  RETURN
229  END IF
230 *
231 * Quick return if possible
232 *
233  IF( m.EQ.0 .OR. n.EQ.0 .OR. k.EQ.0 )
234  \$ RETURN
235 *
236  IF( ( left .AND. .NOT.notran ) .OR. ( .NOT.left .AND. notran ) )
237  \$ THEN
238  i1 = 1
239  i2 = k
240  i3 = 1
241  ELSE
242  i1 = k
243  i2 = 1
244  i3 = -1
245  END IF
246 *
247  IF( left ) THEN
248  ni = n
249  jc = 1
250  ELSE
251  mi = m
252  ic = 1
253  END IF
254 *
255  DO 10 i = i1, i2, i3
256  IF( left ) THEN
257 *
258 * H(i) is applied to C(i:m,1:n)
259 *
260  mi = m - i + 1
261  ic = i
262  ELSE
263 *
264 * H(i) is applied to C(1:m,i:n)
265 *
266  ni = n - i + 1
267  jc = i
268  END IF
269 *
270 * Apply H(i)
271 *
272  aii = a( i, i )
273  a( i, i ) = one
274  CALL slarf( side, mi, ni, a( i, i ), 1, tau( i ), c( ic, jc ),
275  \$ ldc, work )
276  a( i, i ) = aii
277  10 CONTINUE
278  RETURN
279 *
280 * End of SORM2R
281 *
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:62
subroutine slarf(SIDE, M, N, V, INCV, TAU, C, LDC, WORK)
SLARF applies an elementary reflector to a general rectangular matrix.
Definition: slarf.f:126
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:55

Here is the call graph for this function:

Here is the caller graph for this function: