Method optimize_selector_codebook

engine/dlib/src/basis/encoder/basisu_frontend.cpp:674–748

This method will change the number and ordering of the selector codebook clusters.

	// This method will change the number and ordering of the selector codebook clusters.
	void basisu_frontend::optimize_selector_codebook()
	{
		debug_printf("optimize_selector_codebook\n");

		const uint32_t orig_total_selector_clusters = (uint32_t)m_optimized_cluster_selectors.size();

		bool_vec selector_cluster_was_used(m_optimized_cluster_selectors.size());
		for (uint32_t i = 0; i < m_total_blocks; i++)
			selector_cluster_was_used[m_block_selector_cluster_index[i]] = true;

		int_vec old_to_new(m_optimized_cluster_selectors.size());
		int_vec new_to_old;
		uint32_t total_new_entries = 0;

		std::unordered_map<uint32_t, uint32_t> selector_hashmap;

		for (int i = 0; i < static_cast<int>(m_optimized_cluster_selectors.size()); i++)
		{
			if (!selector_cluster_was_used[i])
			{
				old_to_new[i] = -1;
				continue;
			}

			const uint32_t raw_selector_bits = m_optimized_cluster_selectors[i].get_raw_selector_bits();

			auto find_res = selector_hashmap.insert(std::make_pair(raw_selector_bits, total_new_entries));
			if (!find_res.second)
			{
				old_to_new[i] = (find_res.first)->second;
				continue;
			}
						
			old_to_new[i] = total_new_entries++;
			new_to_old.push_back(i);
		}

		debug_printf("Original selector clusters: %u, new cluster selectors: %u\n", orig_total_selector_clusters, total_new_entries);

		for (uint32_t i = 0; i < m_block_selector_cluster_index.size(); i++)
		{
			BASISU_FRONTEND_VERIFY((old_to_new[m_block_selector_cluster_index[i]] >= 0) && (old_to_new[m_block_selector_cluster_index[i]] < (int)total_new_entries));
			m_block_selector_cluster_index[i] = old_to_new[m_block_selector_cluster_index[i]];
		}

		basisu::vector<etc_block> new_optimized_cluster_selectors(m_optimized_cluster_selectors.size() ? total_new_entries : 0);
		basisu::vector<uint_vec> new_selector_cluster_indices(m_selector_cluster_block_indices.size() ? total_new_entries : 0);

		for (uint32_t i = 0; i < total_new_entries; i++)
		{
			if (m_optimized_cluster_selectors.size())
				new_optimized_cluster_selectors[i] = m_optimized_cluster_selectors[new_to_old[i]];

			//if (m_selector_cluster_block_indices.size())
			//	new_selector_cluster_indices[i] = m_selector_cluster_block_indices[new_to_old[i]];
		}

		for (uint32_t i = 0; i < m_block_selector_cluster_index.size(); i++)