205 SUBROUTINE sgebrd( M, N, A, LDA, D, E, TAUQ, TAUP, WORK, LWORK,
214 INTEGER INFO, LDA, LWORK, M, N
217 REAL A( lda, * ), D( * ), E( * ), TAUP( * ),
218 $ tauq( * ), work( * )
225 parameter ( one = 1.0e+0 )
229 INTEGER I, IINFO, J, LDWRKX, LDWRKY, LWKOPT, MINMN, NB,
237 INTRINSIC max, min, real
248 nb = max( 1, ilaenv( 1,
'SGEBRD',
' ', m, n, -1, -1 ) )
250 work( 1 ) =
REAL( lwkopt )
251 lquery = ( lwork.EQ.-1 )
254 ELSE IF( n.LT.0 )
THEN
256 ELSE IF( lda.LT.max( 1, m ) )
THEN
258 ELSE IF( lwork.LT.max( 1, m, n ) .AND. .NOT.lquery )
THEN
262 CALL xerbla(
'SGEBRD', -info )
264 ELSE IF( lquery )
THEN
271 IF( minmn.EQ.0 )
THEN
280 IF( nb.GT.1 .AND. nb.LT.minmn )
THEN
284 nx = max( nb, ilaenv( 3,
'SGEBRD',
' ', m, n, -1, -1 ) )
288 IF( nx.LT.minmn )
THEN
290 IF( lwork.LT.ws )
THEN
295 nbmin = ilaenv( 2,
'SGEBRD',
' ', m, n, -1, -1 )
296 IF( lwork.GE.( m+n )*nbmin )
THEN
308 DO 30 i = 1, minmn - nx, nb
314 CALL slabrd( m-i+1, n-i+1, nb, a( i, i ), lda, d( i ), e( i ),
315 $ tauq( i ), taup( i ), work, ldwrkx,
316 $ work( ldwrkx*nb+1 ), ldwrky )
321 CALL sgemm(
'No transpose',
'Transpose', m-i-nb+1, n-i-nb+1,
322 $ nb, -one, a( i+nb, i ), lda,
323 $ work( ldwrkx*nb+nb+1 ), ldwrky, one,
324 $ a( i+nb, i+nb ), lda )
325 CALL sgemm(
'No transpose',
'No transpose', m-i-nb+1, n-i-nb+1,
326 $ nb, -one, work( nb+1 ), ldwrkx, a( i, i+nb ), lda,
327 $ one, a( i+nb, i+nb ), lda )
332 DO 10 j = i, i + nb - 1
337 DO 20 j = i, i + nb - 1
346 CALL sgebd2( m-i+1, n-i+1, a( i, i ), lda, d( i ), e( i ),
347 $ tauq( i ), taup( i ), work, iinfo )
subroutine sgebd2(M, N, A, LDA, D, E, TAUQ, TAUP, WORK, INFO)
SGEBD2 reduces a general matrix to bidiagonal form using an unblocked algorithm.
subroutine sgemm(TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB, BETA, C, LDC)
SGEMM
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine slabrd(M, N, NB, A, LDA, D, E, TAUQ, TAUP, X, LDX, Y, LDY)
SLABRD reduces the first nb rows and columns of a general matrix to a bidiagonal form.
subroutine sgebrd(M, N, A, LDA, D, E, TAUQ, TAUP, WORK, LWORK, INFO)
SGEBRD