139 SUBROUTINE zgerqf( M, N, A, LDA, TAU, WORK, LWORK, INFO )
147 INTEGER INFO, LDA, LWORK, M, N
150 COMPLEX*16 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,
'ZGERQF',
' ', m, n, -1, -1 )
194 IF( lwork.LT.max( 1, m ) .AND. .NOT.lquery )
THEN
200 CALL xerbla(
'ZGERQF', -info )
202 ELSE IF( lquery )
THEN
215 IF( nb.GT.1 .AND. nb.LT.k )
THEN
219 nx = max( 0, ilaenv( 3,
'ZGERQF',
' ', m, n, -1, -1 ) )
226 IF( lwork.LT.iws )
THEN
232 nbmin = max( 2, ilaenv( 2,
'ZGERQF',
' ', 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 zgerq2( ib, n-k+i+ib-1, a( m-k+i, 1 ), lda, tau( i ),
254 IF( m-k+i.GT.1 )
THEN
259 CALL zlarft(
'Backward',
'Rowwise', n-k+i+ib-1, ib,
260 $ a( m-k+i, 1 ), lda, tau( i ), work, ldwork )
264 CALL zlarfb(
'Right',
'No transpose',
'Backward',
265 $
'Rowwise', m-k+i-1, n-k+i+ib-1, ib,
266 $ a( m-k+i, 1 ), 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 zgerq2( mu, nu, a, lda, tau, work, iinfo )
subroutine zlarft(DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT)
ZLARFT forms the triangular factor T of a block reflector H = I - vtvH
subroutine zgerqf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
ZGERQF
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine zlarfb(SIDE, TRANS, DIRECT, STOREV, M, N, K, V, LDV, T, LDT, C, LDC, WORK, LDWORK)
ZLARFB applies a block reflector or its conjugate-transpose to a general rectangular matrix...
subroutine zgerq2(M, N, A, LDA, TAU, WORK, INFO)
ZGERQ2 computes the RQ factorization of a general rectangular matrix using an unblocked algorithm...