150 SUBROUTINE cgehd2( N, ILO, IHI, A, LDA, TAU, WORK, INFO )
158 INTEGER IHI, ILO, INFO, LDA, N
161 COMPLEX A( lda, * ), TAU( * ), WORK( * )
168 parameter ( one = ( 1.0e+0, 0.0e+0 ) )
178 INTRINSIC conjg, max, min
187 ELSE IF( ilo.LT.1 .OR. ilo.GT.max( 1, n ) )
THEN
189 ELSE IF( ihi.LT.min( ilo, n ) .OR. ihi.GT.n )
THEN
191 ELSE IF( lda.LT.max( 1, n ) )
THEN
195 CALL xerbla(
'CGEHD2', -info )
199 DO 10 i = ilo, ihi - 1
204 CALL clarfg( ihi-i, alpha, a( min( i+2, n ), i ), 1, tau( i ) )
209 CALL clarf(
'Right', ihi, ihi-i, a( i+1, i ), 1, tau( i ),
210 $ a( 1, i+1 ), lda, work )
214 CALL clarf(
'Left', ihi-i, n-i, a( i+1, i ), 1,
215 $ conjg( tau( i ) ), a( i+1, i+1 ), lda, work )
subroutine clarfg(N, ALPHA, X, INCX, TAU)
CLARFG generates an elementary reflector (Householder matrix).
subroutine cgehd2(N, ILO, IHI, A, LDA, TAU, WORK, INFO)
CGEHD2 reduces a general square matrix to upper Hessenberg form using an unblocked algorithm...
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine clarf(SIDE, M, N, V, INCV, TAU, C, LDC, WORK)
CLARF applies an elementary reflector to a general rectangular matrix.