148 SUBROUTINE slags2( UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU,
158 REAL A1, A2, A3, B1, B2, B3, CSQ, CSU, CSV, SNQ,
166 PARAMETER ( ZERO = 0.0e+0 )
169 REAL A, AUA11, AUA12, AUA21, AUA22, AVB11, AVB12,
170 $ AVB21, AVB22, CSL, CSR, D, S1, S2, SNL,
171 $ snr, ua11r, ua22r, vb11r, vb22r, b, c, r, ua11,
172 $ ua12, ua21, ua22, vb11, vb12, vb21, vb22
198 CALL slasv2( a, b, d, s1, s2, snr, csr, snl, csl )
200 IF( abs( csl ).GE.abs( snl ) .OR. abs( csr ).GE.abs( snr ) )
207 ua12 = csl*a2 + snl*a3
210 vb12 = csr*b2 + snr*b3
212 aua12 = abs( csl )*abs( a2 ) + abs( snl )*abs( a3 )
213 avb12 = abs( csr )*abs( b2 ) + abs( snr )*abs( b3 )
217 IF( ( abs( ua11r )+abs( ua12 ) ).NE.zero )
THEN
218 IF( aua12 / ( abs( ua11r )+abs( ua12 ) ).LE.avb12 /
219 $ ( abs( vb11r )+abs( vb12 ) ) )
THEN
220 CALL slartg( -ua11r, ua12, csq, snq, r )
222 CALL slartg( -vb11r, vb12, csq, snq, r )
225 CALL slartg( -vb11r, vb12, csq, snq, r )
239 ua22 = -snl*a2 + csl*a3
242 vb22 = -snr*b2 + csr*b3
244 aua22 = abs( snl )*abs( a2 ) + abs( csl )*abs( a3 )
245 avb22 = abs( snr )*abs( b2 ) + abs( csr )*abs( b3 )
249 IF( ( abs( ua21 )+abs( ua22 ) ).NE.zero )
THEN
250 IF( aua22 / ( abs( ua21 )+abs( ua22 ) ).LE.avb22 /
251 $ ( abs( vb21 )+abs( vb22 ) ) )
THEN
252 CALL slartg( -ua21, ua22, csq, snq, r )
254 CALL slartg( -vb21, vb22, csq, snq, r )
257 CALL slartg( -vb21, vb22, csq, snq, r )
283 CALL slasv2( a, c, d, s1, s2, snr, csr, snl, csl )
285 IF( abs( csr ).GE.abs( snr ) .OR. abs( csl ).GE.abs( snl ) )
291 ua21 = -snr*a1 + csr*a2
294 vb21 = -snl*b1 + csl*b2
297 aua21 = abs( snr )*abs( a1 ) + abs( csr )*abs( a2 )
298 avb21 = abs( snl )*abs( b1 ) + abs( csl )*abs( b2 )
302 IF( ( abs( ua21 )+abs( ua22r ) ).NE.zero )
THEN
303 IF( aua21 / ( abs( ua21 )+abs( ua22r ) ).LE.avb21 /
304 $ ( abs( vb21 )+abs( vb22r ) ) )
THEN
305 CALL slartg( ua22r, ua21, csq, snq, r )
307 CALL slartg( vb22r, vb21, csq, snq, r )
310 CALL slartg( vb22r, vb21, csq, snq, r )
323 ua11 = csr*a1 + snr*a2
326 vb11 = csl*b1 + snl*b2
329 aua11 = abs( csr )*abs( a1 ) + abs( snr )*abs( a2 )
330 avb11 = abs( csl )*abs( b1 ) + abs( snl )*abs( b2 )
334 IF( ( abs( ua11 )+abs( ua12 ) ).NE.zero )
THEN
335 IF( aua11 / ( abs( ua11 )+abs( ua12 ) ).LE.avb11 /
336 $ ( abs( vb11 )+abs( vb12 ) ) )
THEN
337 CALL slartg( ua12, ua11, csq, snq, r )
339 CALL slartg( vb12, vb11, csq, snq, r )
342 CALL slartg( vb12, vb11, csq, snq, r )
subroutine slags2(upper, a1, a2, a3, b1, b2, b3, csu, snu, csv, snv, csq, snq)
SLAGS2 computes 2-by-2 orthogonal matrices U, V, and Q, and applies them to matrices A and B such tha...