139 SUBROUTINE dgeqlf( M, N, A, LDA, TAU, WORK, LWORK, INFO )
147 INTEGER INFO, LDA, LWORK, M, N
150 DOUBLE PRECISION A( lda, * ), TAU( * ), WORK( * )
157 INTEGER I, IB, IINFO, IWS, K, KI, KK, LDWORK, LWKOPT,
158 $ mu, nb, nbmin, nu, nx
175 lquery = ( lwork.EQ.-1 )
178 ELSE IF( n.LT.0 )
THEN
180 ELSE IF( lda.LT.max( 1, m ) )
THEN
189 nb = ilaenv( 1,
'DGEQLF',
' ', m, n, -1, -1 )
194 IF( lwork.LT.max( 1, n ) .AND. .NOT.lquery )
THEN
200 CALL xerbla(
'DGEQLF', -info )
202 ELSE IF( lquery )
THEN
215 IF( nb.GT.1 .AND. nb.LT.k )
THEN
219 nx = max( 0, ilaenv( 3,
'DGEQLF',
' ', m, n, -1, -1 ) )
226 IF( lwork.LT.iws )
THEN
232 nbmin = max( 2, ilaenv( 2,
'DGEQLF',
' ', m, n, -1,
238 IF( nb.GE.nbmin .AND. nb.LT.k .AND. nx.LT.k )
THEN
243 ki = ( ( k-nx-1 ) / nb )*nb
246 DO 10 i = k - kk + ki + 1, k - kk + 1, -nb
247 ib = min( k-i+1, nb )
252 CALL dgeql2( m-k+i+ib-1, ib, a( 1, n-k+i ), lda, tau( i ),
254 IF( n-k+i.GT.1 )
THEN
259 CALL dlarft(
'Backward',
'Columnwise', m-k+i+ib-1, ib,
260 $ a( 1, n-k+i ), lda, tau( i ), work, ldwork )
264 CALL dlarfb(
'Left',
'Transpose',
'Backward',
265 $
'Columnwise', m-k+i+ib-1, n-k+i-1, ib,
266 $ a( 1, n-k+i ), lda, work, ldwork, a, lda,
267 $ work( ib+1 ), ldwork )
270 mu = m - k + i + nb - 1
271 nu = n - k + i + nb - 1
279 IF( mu.GT.0 .AND. nu.GT.0 )
280 $
CALL dgeql2( mu, nu, a, lda, tau, work, iinfo )
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 dgeqlf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
DGEQLF
subroutine dgeql2(M, N, A, LDA, TAU, WORK, INFO)
DGEQL2 computes the QL factorization of a general rectangular matrix using an unblocked algorithm...
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 xerbla(SRNAME, INFO)
XERBLA