Function enterOneStrongPolyShift

kernel/GBEngine/kutil.cc:11638–11799

*/
#ifdef HAVE_SHIFTBBA
static BOOLEAN enterOneStrongPolyShift (poly q, poly p, int /*ecart*/, int /*isFromQ*/, kStrategy strat, int atR, int /*ecartq*/, int /*qisFromQ*/, int shiftcount, int ifromS)
{
  number d, s, t;
  /* assume(atR >= 0); */
  assume(ifromS <= strat->sl);
  assume(rField_is_Ring(currRing));
  poly m1, m2, gcd;
  //printf("\n--------------------------------\n");
  //pWrite(p);pWrite(si);
  d = n_ExtGcd(pGetCoeff(p), pGetCoeff(q), &s, &t, currRing->cf);

  if (nIsZero(s) || nIsZero(t))  // evtl. durch divBy tests ersetzen
  {
    nDelete(&d);
    nDelete(&s);
    nDelete(&t);
    return FALSE;
  }

  assume(pIsInV(p));

  k_GetStrongLeadTerms(p, q, currRing, m1, m2, gcd, strat->tailRing);

  /* the V criterion */
  if (!pmIsInV(gcd))
  {
    strat->cv++;
    nDelete(&d);
    nDelete(&s);
    nDelete(&t);
    pLmFree(gcd);
    return FALSE;
  }

  // disabled for Letterplace because it is not so easy to check
  /* if (!rHasLocalOrMixedOrdering(currRing)) { */
  /*   unsigned long sev = pGetShortExpVector(gcd); */

  /*   for (int j = 0; j < strat->sl; j++) { */
  /*     if (j == i) */
  /*       continue; */

  /*     if (n_DivBy(d, pGetCoeff(strat->S[j]), currRing->cf) && */
  /*         !(strat->sevS[j] & ~sev) && */
  /*         p_LmDivisibleBy(strat->S[j], gcd, currRing)) { */
  /*       nDelete(&d); */
  /*       nDelete(&s); */
  /*       nDelete(&t); */
  /*       return FALSE; */
  /*     } */
  /*   } */
  /* } */

  poly m12, m22;
  assume(p_mFirstVblock(p, currRing) <= 1 || p_mFirstVblock(q, currRing) <= 1);
  k_SplitFrame(m1, m12, si_max(p_mFirstVblock(p, currRing), 1), currRing);
  k_SplitFrame(m2, m22, si_max(p_mFirstVblock(q, currRing), 1), currRing);
  // manually free the coeffs, because pSetCoeff0 is used in the next step