145 SUBROUTINE cgeqrf( M, N, A, LDA, TAU, WORK, LWORK, INFO )
152 INTEGER INFO, LDA, LWORK, M, N
155 COMPLEX A( LDA, * ), TAU( * ), WORK( * )
162 INTEGER I, IB, IINFO, IWS, K, LDWORK, LWKOPT, NB,
181 nb = ilaenv( 1,
'CGEQRF',
' ', m, n, -1, -1 )
182 lquery = ( lwork.EQ.-1 )
185 ELSE IF( n.LT.0 )
THEN
187 ELSE IF( lda.LT.max( 1, m ) )
THEN
189 ELSE IF( .NOT.lquery )
THEN
190 IF( lwork.LE.0 .OR. ( m.GT.0 .AND. lwork.LT.max( 1, n ) ) )
194 CALL xerbla(
'CGEQRF', -info )
196 ELSE IF( lquery )
THEN
216 IF( nb.GT.1 .AND. nb.LT.k )
THEN
220 nx = max( 0, ilaenv( 3,
'CGEQRF',
' ', m, n, -1, -1 ) )
227 IF( lwork.LT.iws )
THEN
233 nbmin = max( 2, ilaenv( 2,
'CGEQRF',
' ', m, n, -1,
239 IF( nb.GE.nbmin .AND. nb.LT.k .AND. nx.LT.k )
THEN
243 DO 10 i = 1, k - nx, nb
244 ib = min( k-i+1, nb )
249 CALL cgeqr2( m-i+1, ib, a( i, i ), lda, tau( i ), work,
256 CALL clarft(
'Forward',
'Columnwise', m-i+1, ib,
257 $ a( i, i ), lda, tau( i ), work, ldwork )
261 CALL clarfb(
'Left',
'Conjugate transpose',
'Forward',
262 $
'Columnwise', m-i+1, n-i-ib+1, ib,
263 $ a( i, i ), lda, work, ldwork, a( i, i+ib ),
264 $ lda, work( ib+1 ), ldwork )
274 $
CALL cgeqr2( m-i+1, n-i+1, a( i, i ), lda, tau( i ), work,
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine cgeqr2(M, N, A, LDA, TAU, WORK, INFO)
CGEQR2 computes the QR factorization of a general rectangular matrix using an unblocked algorithm.
subroutine cgeqrf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
CGEQRF
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.
subroutine clarft(DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT)
CLARFT forms the triangular factor T of a block reflector H = I - vtvH