Function GFMapDown

factory/cf_map_ext.cc:277–286

}

CanonicalForm GFMapDown (const CanonicalForm & F, int k)
{
  int d= getGFDegree();
  ASSERT (d % k == 0, "multiple of GF degree expected");
  int p= getCharacteristic();
  int ext_field_size= ipower (p, d);
  int field_size= ipower ( p, k);
  int diff= (ext_field_size - 1)/(field_size - 1);
  return GFPowDown (F, diff);
}

/// map F in \f$ F_{p} (\alpha ) \f$ which is generated by G into some
/// \f$ F_{p}(\beta ) \f$ which is generated by H