Function sparseGCDFp

factory/cfModGcd.cc:3570–4076

}

CanonicalForm sparseGCDFp (const CanonicalForm& F, const CanonicalForm& G,
                           bool& topLevel, CFList& l)
{
  CanonicalForm A= F;
  CanonicalForm B= G;
  if (F.isZero() && degree(G) > 0) return G/Lc(G);
  else if (G.isZero() && degree (F) > 0) return F/Lc(F);
  else if (F.isZero() && G.isZero()) return F.genOne();
  if (F.inBaseDomain() || G.inBaseDomain()) return F.genOne();
  if (F.isUnivariate() && fdivides(F, G)) return F/Lc(F);
  if (G.isUnivariate() && fdivides(G, F)) return G/Lc(G);
  if (F == G) return F/Lc(F);

  CFMap M,N;
  int best_level= myCompress (A, B, M, N, topLevel);

  if (best_level == 0) return B.genOne();

  A= M(A);
  B= M(B);

  Variable x= Variable (1);

  //univariate case
  if (A.isUnivariate() && B.isUnivariate())
    return N (gcd (A, B));

  CanonicalForm cA, cB;    // content of A and B
  CanonicalForm ppA, ppB;    // primitive part of A and B
  CanonicalForm gcdcAcB;

  cA = uni_content (A);
  cB = uni_content (B);
  gcdcAcB= gcd (cA, cB);
  ppA= A/cA;
  ppB= B/cB;

  CanonicalForm lcA, lcB;  // leading coefficients of A and B
  CanonicalForm gcdlcAlcB;
  lcA= uni_lcoeff (ppA);
  lcB= uni_lcoeff (ppB);

  if (fdivides (lcA, lcB))
  {
    if (fdivides (A, B))
      return F/Lc(F);
  }
  if (fdivides (lcB, lcA))
  {
    if (fdivides (B, A))
      return G/Lc(G);
  }

  gcdlcAlcB= gcd (lcA, lcB);

  int d= totaldegree (ppA, Variable (2), Variable (ppA.level()));
  int d0;