169 SUBROUTINE sgehrd( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO )
177 INTEGER ihi, ilo, info, lda, lwork, n
180 REAL a( lda, * ), tau( * ), work( * )
187 parameter( nbmax = 64, ldt = nbmax+1 )
189 parameter( zero = 0.0e+0,
194 INTEGER i, ib, iinfo, iws,
j, ldwork, lwkopt, nb,
217 nb = min( nbmax,
ilaenv( 1,
'SGEHRD',
' ', n, ilo, ihi, -1 ) )
220 lquery = ( lwork.EQ.-1 )
223 ELSE IF( ilo.LT.1 .OR. ilo.GT.max( 1, n ) )
THEN
225 ELSE IF( ihi.LT.min( ilo, n ) .OR. ihi.GT.n )
THEN
227 ELSE IF( lda.LT.max( 1, n ) )
THEN
229 ELSE IF( lwork.LT.max( 1, n ) .AND. .NOT.lquery )
THEN
233 CALL
xerbla(
'SGEHRD', -info )
235 ELSE IF( lquery )
THEN
244 DO 20 i = max( 1, ihi ), n - 1
258 nb = min( nbmax,
ilaenv( 1,
'SGEHRD',
' ', n, ilo, ihi, -1 ) )
261 IF( nb.GT.1 .AND. nb.LT.nh )
THEN
266 nx = max( nb,
ilaenv( 3,
'SGEHRD',
' ', n, ilo, ihi, -1 ) )
272 IF( lwork.LT.iws )
THEN
278 nbmin = max( 2,
ilaenv( 2,
'SGEHRD',
' ', n, ilo, ihi,
280 IF( lwork.GE.n*nbmin )
THEN
290 IF( nb.LT.nbmin .OR. nb.GE.nh )
THEN
300 DO 40 i = ilo, ihi - 1 - nx, nb
301 ib = min( nb, ihi-i )
307 CALL
slahr2( ihi, i, ib, a( 1, i ), lda, tau( i ), t, ldt,
314 ei = a( i+ib, i+ib-1 )
315 a( i+ib, i+ib-1 ) = one
316 CALL
sgemm(
'No transpose',
'Transpose',
318 $ ib, -one, work, ldwork, a( i+ib, i ), lda, one,
319 $ a( 1, i+ib ), lda )
320 a( i+ib, i+ib-1 ) = ei
325 CALL
strmm(
'Right',
'Lower',
'Transpose',
327 $ one, a( i+1, i ), lda, work, ldwork )
329 CALL
saxpy( i, -one, work( ldwork*
j+1 ), 1,
336 CALL
slarfb(
'Left',
'Transpose',
'Forward',
338 $ ihi-i, n-i-ib+1, ib, a( i+1, i ), lda, t, ldt,
339 $ a( i+1, i+ib ), lda, work, ldwork )
345 CALL
sgehd2( n, i, ihi, a, lda, tau, work, iinfo )
subroutine slahr2(N, K, NB, A, LDA, TAU, T, LDT, Y, LDY)
SLAHR2 reduces the specified number of first columns of a general rectangular matrix A so that elemen...
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine saxpy(N, SA, SX, INCX, SY, INCY)
SAXPY
subroutine strmm(SIDE, UPLO, TRANSA, DIAG, M, N, ALPHA, A, LDA, B, LDB)
STRMM
subroutine sgehd2(N, ILO, IHI, A, LDA, TAU, WORK, INFO)
SGEHD2 reduces a general square matrix to upper Hessenberg form using an unblocked algorithm...
subroutine sgemm(TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB, BETA, C, LDC)
SGEMM
set ue cd $ADTTMP cat<< EOF > tmp f Program LinearEquations Implicit none Real j
integer function ilaenv(ISPEC, NAME, OPTS, N1, N2, N3, N4)
subroutine sgehrd(N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
SGEHRD
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.