Method updateWeakArray

src/TopicModel/TopicModel.hpp:482–494

		}

		void updateWeakArray()
		{
			wOffsetByDoc.emplace_back(0);
			for (auto& doc : docs)
			{
				wOffsetByDoc.emplace_back(wOffsetByDoc.back() + doc.words.size());
			}
			auto tx = [](_DocType& doc) { return &doc.words; };
			tvector<Vid>::trade(words, 
				makeTransformIter(docs.begin(), tx),
				makeTransformIter(docs.end(), tx)
			);
		}

		void updateForCopy()
		{