137 SUBROUTINE dgeqrf( M, N, A, LDA, TAU, WORK, LWORK, INFO )
145 INTEGER INFO, LDA, LWORK, M, N
148 DOUBLE PRECISION A( lda, * ), TAU( * ), WORK( * )
155 INTEGER I, IB, IINFO, IWS, K, LDWORK, LWKOPT, NB,
173 nb = ilaenv( 1,
'DGEQRF',
' ', 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(
'DGEQRF', -info )
189 ELSE IF( lquery )
THEN
204 IF( nb.GT.1 .AND. nb.LT.k )
THEN
208 nx = max( 0, ilaenv( 3,
'DGEQRF',
' ', m, n, -1, -1 ) )
215 IF( lwork.LT.iws )
THEN
221 nbmin = max( 2, ilaenv( 2,
'DGEQRF',
' ', 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 dgeqr2( m-i+1, ib, a( i, i ), lda, tau( i ), work,
244 CALL dlarft(
'Forward',
'Columnwise', m-i+1, ib,
245 $ a( i, i ), lda, tau( i ), work, ldwork )
249 CALL dlarfb(
'Left',
'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 dgeqr2( m-i+1, n-i+1, a( i, i ), lda, tau( i ), work,
subroutine dlarft(DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT)
DLARFT forms the triangular factor T of a block reflector H = I - vtvH
subroutine dlarfb(SIDE, TRANS, DIRECT, STOREV, M, N, K, V, LDV, T, LDT, C, LDC, WORK, LDWORK)
DLARFB applies a block reflector or its transpose to a general rectangular matrix.
subroutine dgeqrf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
DGEQRF
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine dgeqr2(M, N, A, LDA, TAU, WORK, INFO)
DGEQR2 computes the QR factorization of a general rectangular matrix using an unblocked algorithm...