popular_var()

int popular_var ( const MonomialIdeal & I, int & npure, exponents_t pure, int & nhits, const_varpower & non_pure_power, int & exp_of_popular )

static

Definition at line 172 of file hilb.cpp.

{
  int k;
  npure = 0;
  int nvars = I.topvar() + 1;
  for (k = 0; k < nvars; k++) pure[k] = -1;
 
  exponents_t hits = newarray_atomic_clear(int, nvars);
  exponents_t minnonzero = newarray_atomic(int, nvars);
  for (k = 0; k < nvars; k++) hits[k] = 0;
  for (k = 0; k < nvars; k++) minnonzero[k] = MAX_EXP;
 
  non_pure_power = nullptr;
 
  for (Bag& a : I)
    {
      const_varpower m = a.monom().data();
      index_varpower j = m;
      assert(j.valid());  // The monomial cannot be '1'.
      int v = j.var();
      int e = j.exponent();
      ++j;
      if (j.valid())
        {
          non_pure_power = m;
          for (; j.valid(); ++j)
            {
              v = j.var();
              e = j.exponent();
              if (minnonzero[v] > e) minnonzero[v] = e;
              hits[v]++;
            }
        }
      else
        {
          if (pure[v] == -1)
            {
              npure++;
              pure[v] = e;
            }
          else if (pure[v] > e)
            pure[v] = e;
        }
    }
 
  int popular = 0;
  for (k = 1; k < nvars; k++)
    if (hits[k] > hits[popular]) popular = k;
  nhits = hits[popular];
  exp_of_popular = minnonzero[popular];
  freemem(hits);
  freemem(minnonzero);
  return popular;
}

References ExponentListIterator< E, L >::exponent(), freemem(), MAX_EXP, newarray_atomic, newarray_atomic_clear, MonomialIdeal::topvar(), ExponentListIterator< E, L >::valid(), and ExponentListIterator< E, L >::var().

Referenced by find_pivot().