142 SUBROUTINE sgeqrt( M, N, NB, A, LDA, T, LDT, WORK, INFO )
150 INTEGER INFO, LDA, LDT, M, N, NB
153 REAL A( lda, * ), T( ldt, * ), WORK( * )
160 INTEGER I, IB, IINFO, K
161 LOGICAL USE_RECURSIVE_QR
162 parameter( use_recursive_qr=.true. )
174 ELSE IF( n.LT.0 )
THEN
176 ELSE IF( nb.LT.1 .OR. ( nb.GT.min(m,n) .AND. min(m,n).GT.0 ) )
THEN
178 ELSE IF( lda.LT.max( 1, m ) )
THEN
180 ELSE IF( ldt.LT.nb )
THEN
184 CALL xerbla(
'SGEQRT', -info )
196 ib = min( k-i+1, nb )
200 IF( use_recursive_qr )
THEN
201 CALL sgeqrt3( m-i+1, ib, a(i,i), lda, t(1,i), ldt, iinfo )
203 CALL sgeqrt2( m-i+1, ib, a(i,i), lda, t(1,i), ldt, iinfo )
209 CALL slarfb(
'L',
'T',
'F',
'C', m-i+1, n-i-ib+1, ib,
210 $ a( i, i ), lda, t( 1, i ), ldt,
211 $ a( i, i+ib ), lda, work , n-i-ib+1 )
subroutine sgeqrt2(M, N, A, LDA, T, LDT, INFO)
SGEQRT2 computes a QR factorization of a general real or complex matrix using the compact WY represen...
subroutine sgeqrt(M, N, NB, A, LDA, T, LDT, WORK, INFO)
SGEQRT
subroutine xerbla(SRNAME, INFO)
XERBLA
recursive subroutine sgeqrt3(M, N, A, LDA, T, LDT, INFO)
SGEQRT3 recursively computes a QR factorization of a general real or complex matrix using the compact...
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.