145 SUBROUTINE sgeqrf( M, N, A, LDA, TAU, WORK, LWORK, INFO )
152 INTEGER INFO, LDA, LWORK, M, N
155 REAL A( LDA, * ), TAU( * ), WORK( * )
162 INTEGER I, IB, IINFO, IWS, K, LDWORK, LWKOPT, NB,
181 nb = ilaenv( 1,
'SGEQRF',
' ', 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(
'SGEQRF', -info )
196 ELSE IF( lquery )
THEN
216 IF( nb.GT.1 .AND. nb.LT.k )
THEN
220 nx = max( 0, ilaenv( 3,
'SGEQRF',
' ', m, n, -1, -1 ) )
227 IF( lwork.LT.iws )
THEN
233 nbmin = max( 2, ilaenv( 2,
'SGEQRF',
' ', 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 sgeqr2( m-i+1, ib, a( i, i ), lda, tau( i ), work,
256 CALL slarft(
'Forward',
'Columnwise', m-i+1, ib,
257 $ a( i, i ), lda, tau( i ), work, ldwork )
261 CALL slarfb(
'Left',
'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 sgeqr2( m-i+1, n-i+1, a( i, i ), lda, tau( i ), work,
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine sgeqrf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
SGEQRF
subroutine sgeqr2(M, N, A, LDA, TAU, WORK, INFO)
SGEQR2 computes the QR factorization of a general rectangular matrix using an unblocked algorithm.
subroutine slarfb(SIDE, TRANS, DIRECT, STOREV, M, N, K, V, LDV, T, LDT, C, LDC, WORK, LDWORK)
SLARFB applies a block reflector or its transpose to a general rectangular matrix.
subroutine slarft(DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT)
SLARFT forms the triangular factor T of a block reflector H = I - vtvH