void cpc_union_alloc::reduce_k()

in cpc/include/cpc_union_impl.hpp [312:346]

• 30 lines of code
• 11 McCabe index (conditional complexity)

void cpc_union_alloc<A>::reduce_k(uint8_t new_lg_k) {
  if (new_lg_k >= lg_k) throw std::logic_error("new LgK >= union lgK");
  if (accumulator == nullptr && bit_matrix.size() == 0) throw std::logic_error("both accumulator and bit_matrix are absent");

  if (bit_matrix.size() > 0) { // downsample the unioner's bit matrix
    if (accumulator != nullptr) throw std::logic_error("accumulator is not null");
    vector_u64<A> old_matrix = std::move(bit_matrix);
    const uint8_t old_lg_k = lg_k;
    const uint32_t new_k = 1 << new_lg_k;
    bit_matrix = vector_u64<A>(new_k, 0, old_matrix.get_allocator());
    lg_k = new_lg_k;
    or_matrix_into_matrix(old_matrix, old_lg_k);
    return;
  }

  if (accumulator != nullptr) { // downsample the unioner's sketch
    if (bit_matrix.size() > 0) throw std::logic_error("bit_matrix is not expected");
    if (!accumulator->is_empty()) {
      cpc_sketch_alloc<A> old_accumulator(*accumulator);
      *accumulator = cpc_sketch_alloc<A>(new_lg_k, seed, old_accumulator.get_allocator());
      walk_table_updating_sketch(old_accumulator.surprising_value_table);
    }
    lg_k = new_lg_k;

    const auto final_new_flavor = accumulator->determine_flavor();
    // if the new sketch has graduated beyond sparse, convert to bit_matrix
    if (final_new_flavor != cpc_sketch_alloc<A>::flavor::EMPTY &&
        final_new_flavor != cpc_sketch_alloc<A>::flavor::SPARSE) {
      switch_to_bit_matrix();
    }
    return;
  }

  throw std::logic_error("invalid state");
}