Function idLiftStd

kernel/ideals.cc:976–1039

*computes a standard basis for h1 and stores the transformation matrix * in ma */

* in ma
*/
ideal idLiftStd (ideal  h1, matrix* T, tHomog hi, ideal * S, GbVariant alg,
  ideal h11)
{
  int  inputIsIdeal=id_RankFreeModule(h1,currRing);
  long k;
  intvec *w=NULL;

  idDelete((ideal*)T);
  BOOLEAN lift3=FALSE;
  if (S!=NULL) { lift3=TRUE; idDelete(S); }
  if (idIs0(h1))
  {
    *T=mpNew(1,IDELEMS(h1));
    if (lift3)
    {
      *S=idFreeModule(IDELEMS(h1));
    }
    return idInit(1,h1->rank);
  }

  BITSET save2;
  SI_SAVE_OPT2(save2);

  k=si_max(1,inputIsIdeal);

  if ((!lift3)&&(!TEST_OPT_RETURN_SB)) si_opt_2 |=Sy_bit(V_IDLIFT);

  ring orig_ring = currRing;
  ring syz_ring = rAssure_SyzOrder(orig_ring,TRUE);
  rSetSyzComp(k,syz_ring);
  rChangeCurrRing(syz_ring);

  ideal s_h1;

  if (orig_ring != syz_ring)
    s_h1 = idrCopyR_NoSort(h1,orig_ring,syz_ring);
  else
    s_h1 = h1;
  ideal s_h11=NULL;
  if (h11!=NULL)
  {
    s_h11=idrCopyR_NoSort(h11,orig_ring,syz_ring);
  }


  ideal s_h3=idPrepare(s_h1,s_h11,hi,k,&w,alg); // main (syz) GB computation


  if (w!=NULL) delete w;
  if (syz_ring!=orig_ring)
  {
    idDelete(&s_h1);
    if (s_h11!=NULL) idDelete(&s_h11);
  }

  if (S!=NULL) (*S)=idInit(IDELEMS(s_h3),IDELEMS(h1));

  s_h3=idExtractG_T_S(s_h3,T,S,k,IDELEMS(h1),inputIsIdeal,orig_ring,syz_ring);