Function MwalkAlt

Singular/walk.cc:5028–5298

THE NEW GROEBNER WALK ALGORITHM Groebnerwalk with a recursive "second" alternative GW, called REC_GB_Mwalk that only computes the last reduced GB

// THE NEW GROEBNER WALK ALGORITHM
// Groebnerwalk with a recursive "second" alternative GW, called REC_GB_Mwalk that only computes the last reduced GB
ideal MwalkAlt(ideal Go, intvec* curr_weight, intvec* target_weight)
{
  Set_Error(FALSE);
  Overflow_Error = FALSE;
  //Print("// pSetm_Error = (%d)", ErrorCheck());

#ifdef TIME_TEST
  clock_t tinput, tostd, tif=0, tstd=0, tlift=0, tred=0, tnw=0;
  tinput = clock();
  clock_t tim;
  xtif=0; xtstd=0; xtlift=0; xtred=0; xtnw=0;
#endif
  nstep=0;
  int i;
  int nV = currRing->N;
  int nwalk=0;
  int endwalks=0;

  ideal Gomega, M, F, Gomega1, Gomega2, M1, F1, G;

  ring newRing, oldRing;
  intvec* ivNull = new intvec(nV);
  intvec* exivlp = Mivlp(nV);
#ifndef BUCHBERGER_ALG
  intvec* hilb_func;
#endif
  intvec* tmp_weight = new intvec(nV);
  for(i=nV-1; i>=0; i--)
    (*tmp_weight)[i] = (*curr_weight)[i];

   // to avoid (1,0,...,0) as the target vector
  intvec* last_omega = new intvec(nV);
  for(i=nV-1; i>0; i--)
    (*last_omega)[i] = 1;
  (*last_omega)[0] = 10000;

  ring XXRing = currRing;

#ifdef TIME_TEST
  to = clock();
#endif
  // the monomial ordering of this current ring would be "dp"
  G = MstdCC(Go);
#ifdef TIME_TEST
  tostd = clock()-to;
#endif

  if(currRing->order[0] == ringorder_a)
    goto NEXT_VECTOR;

  while(1)
  {
    nwalk ++;
    nstep ++;
#ifdef TIME_TEST
    to = clock();
#endif
    // compute an initial form ideal of <G> w.r.t. "curr_vector"