Function myCompress

factory/cfModGcd.cc:92–254

compressing two polynomials F and G, M is used for compressing, N to reverse the compression

/// compressing two polynomials F and G, M is used for compressing,
/// N to reverse the compression
int myCompress (const CanonicalForm& F, const CanonicalForm& G, CFMap & M,
                CFMap & N, bool topLevel)
{
  int n= tmax (F.level(), G.level());
  int * degsf= NEW_ARRAY(int,n + 1);
  int * degsg= NEW_ARRAY(int,n + 1);

  for (int i = n; i >= 0; i--)
    degsf[i]= degsg[i]= 0;

  degsf= degrees (F, degsf);
  degsg= degrees (G, degsg);

  int both_non_zero= 0;
  int f_zero= 0;
  int g_zero= 0;
  int both_zero= 0;

  if (topLevel)
  {
    for (int i= 1; i <= n; i++)
    {
      if (degsf[i] != 0 && degsg[i] != 0)
      {
        both_non_zero++;
        continue;
      }
      if (degsf[i] == 0 && degsg[i] != 0 && i <= G.level())
      {
        f_zero++;
        continue;
      }
      if (degsg[i] == 0 && degsf[i] && i <= F.level())
      {
        g_zero++;
        continue;
      }
    }

    if (both_non_zero == 0)
    {
      DELETE_ARRAY(degsf);
      DELETE_ARRAY(degsg);
      return 0;
    }

    // map Variables which do not occur in both polynomials to higher levels
    int k= 1;
    int l= 1;
    for (int i= 1; i <= n; i++)
    {
      if (degsf[i] != 0 && degsg[i] == 0 && i <= F.level())
      {
        if (k + both_non_zero != i)
        {
          M.newpair (Variable (i), Variable (k + both_non_zero));
          N.newpair (Variable (k + both_non_zero), Variable (i));
        }