122 SUBROUTINE sgeqr2( M, N, A, LDA, TAU, WORK, INFO )
130 INTEGER INFO, LDA, M, N
133 REAL A( lda, * ), TAU( * ), WORK( * )
140 parameter ( one = 1.0e+0 )
159 ELSE IF( n.LT.0 )
THEN
161 ELSE IF( lda.LT.max( 1, m ) )
THEN
165 CALL xerbla(
'SGEQR2', -info )
175 CALL slarfg( m-i+1, a( i, i ), a( min( i+1, m ), i ), 1,
183 CALL slarf(
'Left', m-i+1, n-i, a( i, i ), 1, tau( i ),
184 $ a( i, i+1 ), lda, work )
subroutine sgeqr2(M, N, A, LDA, TAU, WORK, INFO)
SGEQR2 computes the QR factorization of a general rectangular matrix using an unblocked algorithm...
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine slarfg(N, ALPHA, X, INCX, TAU)
SLARFG generates an elementary reflector (Householder matrix).
subroutine slarf(SIDE, M, N, V, INCV, TAU, C, LDC, WORK)
SLARF applies an elementary reflector to a general rectangular matrix.