135 SUBROUTINE sgetrf( M, N, A, LDA, IPIV, INFO )
143 INTEGER info, lda, m, n
153 REAL one, zero, negone
154 parameter( one = 1.0e+0, zero = 0.0e+0 )
155 parameter( negone = -1.0e+0 )
159 INTEGER i,
j, jp, nstep, ntopiv, npived, kahead
160 INTEGER kstart, ipivstart, jpivstart, kcols
172 INTRINSIC max, min, iand
181 ELSE IF( n.LT.0 )
THEN
183 ELSE IF( lda.LT.max( 1, m ) )
THEN
187 CALL
xerbla(
'SGETRF', -info )
193 IF( m.EQ.0 .OR. n.EQ.0 )
202 kahead = iand(
j, -
j )
203 kstart =
j + 1 - kahead
204 kcols = min( kahead, m-
j )
214 a(
j,
j ) = a( jp,
j )
221 jpivstart =
j - ntopiv
222 DO WHILE ( ntopiv .LT. kahead )
223 CALL
slaswp( ntopiv, a( 1, jpivstart ), lda, ipivstart,
j,
225 ipivstart = ipivstart - ntopiv;
227 jpivstart = jpivstart - ntopiv;
231 CALL
slaswp( kcols, a( 1,
j+1 ), lda, kstart,
j, ipiv, 1 )
234 IF( a(
j,
j ).NE.zero .AND. .NOT.
sisnan( a(
j,
j ) ) )
THEN
235 IF( abs(a(
j,
j )) .GE. sfmin )
THEN
236 CALL
sscal( m-
j, one / a(
j,
j ), a(
j+1,
j ), 1 )
239 a(
j+i,
j ) = a(
j+i,
j ) / a(
j,
j )
242 ELSE IF( a(
j,
j ) .EQ. zero .AND. info .EQ. 0 )
THEN
247 CALL
strsm(
'Left',
'Lower',
'No transpose',
'Unit', kahead,
248 $ kcols, one, a( kstart, kstart ), lda,
249 $ a( kstart,
j+1 ), lda )
251 CALL
sgemm(
'No transpose',
'No transpose', m-
j,
252 $ kcols, kahead, negone, a(
j+1, kstart ), lda,
253 $ a( kstart,
j+1 ), lda, one, a(
j+1,
j+1 ), lda )
257 npived = iand( nstep, -nstep )
259 DO WHILE (
j .GT. 0 )
260 ntopiv = iand(
j, -
j )
261 CALL
slaswp( ntopiv, a( 1,
j-ntopiv+1 ), lda,
j+1, nstep,
268 CALL
slaswp( n-m, a( 1, m+kcols+1 ), lda, 1, m, ipiv, 1 )
269 CALL
strsm(
'Left',
'Lower',
'No transpose',
'Unit', m,
270 $ n-m, one, a, lda, a( 1,m+kcols+1 ), lda )