137 SUBROUTINE cgeqrf( M, N, A, LDA, TAU, WORK, LWORK, INFO )
145 INTEGER INFO, LDA, LWORK, M, N
148 COMPLEX A( lda, * ), TAU( * ), WORK( * )
155 INTEGER I, IB, IINFO, IWS, K, LDWORK, LWKOPT, NB,
173 nb = ilaenv( 1,
'CGEQRF',
' ', m, n, -1, -1 )
176 lquery = ( lwork.EQ.-1 )
179 ELSE IF( n.LT.0 )
THEN
181 ELSE IF( lda.LT.max( 1, m ) )
THEN
183 ELSE IF( lwork.LT.max( 1, n ) .AND. .NOT.lquery )
THEN
187 CALL xerbla(
'CGEQRF', -info )
189 ELSE IF( lquery )
THEN
204 IF( nb.GT.1 .AND. nb.LT.k )
THEN
208 nx = max( 0, ilaenv( 3,
'CGEQRF',
' ', m, n, -1, -1 ) )
215 IF( lwork.LT.iws )
THEN
221 nbmin = max( 2, ilaenv( 2,
'CGEQRF',
' ', m, n, -1,
227 IF( nb.GE.nbmin .AND. nb.LT.k .AND. nx.LT.k )
THEN
231 DO 10 i = 1, k - nx, nb
232 ib = min( k-i+1, nb )
237 CALL cgeqr2( m-i+1, ib, a( i, i ), lda, tau( i ), work,
244 CALL clarft(
'Forward',
'Columnwise', m-i+1, ib,
245 $ a( i, i ), lda, tau( i ), work, ldwork )
249 CALL clarfb(
'Left',
'Conjugate transpose',
'Forward',
250 $
'Columnwise', m-i+1, n-i-ib+1, ib,
251 $ a( i, i ), lda, work, ldwork, a( i, i+ib ),
252 $ lda, work( ib+1 ), ldwork )
262 $
CALL cgeqr2( m-i+1, n-i+1, a( i, i ), lda, tau( i ), work,
subroutine clarft(DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT)
CLARFT forms the triangular factor T of a block reflector H = I - vtvH
subroutine cgeqr2(M, N, A, LDA, TAU, WORK, INFO)
CGEQR2 computes the QR factorization of a general rectangular matrix using an unblocked algorithm...
subroutine xerbla(SRNAME, INFO)
XERBLA
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...