Machine-Created Universal Language for Cross-lingual Transfer

There are two types of approaches to solving cross-lingual transfer: multilingual pre-training implicitly aligns the hidden representations of different languages, while the translate-test explicitly translates different languages to an intermediate language, such as English. Translate-test has better interpretability compared to multilingual pre-training. However, the translate-test has lower performance than multilingual pre-training(Conneau and Lample, 2019; Conneau et al, 2020) and can't solve word-level tasks because translation rearranges the word order. Therefore, we propose a new Machine-created Universal Language (MUL) as a new intermediate language. MUL consists of a set of discrete symbols as universal vocabulary and NL-MUL translator for translating from multiple natural languages to MUL. MUL unifies common concepts from different languages into the same universal word for better cross-language transfer. And MUL preserves the language-specific words as well as word order, so the model can be easily applied to word-level tasks. Our experiments show that translating into MUL achieves better performance compared to multilingual pre-training, and our analyses show that MUL has good interpretability.

Sparse Double Descent: Where Network Pruning Aggravates Overfitting

People usually believe that network pruning not only reduces the computational cost of deep networks, but also prevents overfitting by decreasing model capacity. However, our work surprisingly discovers that network pruning sometimes even aggravates overfitting. We report an unexpected sparse double descent phenomenon that, as we increase model sparsity via network pruning, test performance first gets worse (due to overfitting), then gets better (due to relieved overfitting), and gets worse at last (due to forgetting useful information). While recent studies focused on the deep double descent with respect to model overparameterization, they failed to recognize that sparsity may also cause double descent. In this paper, we have three main contributions. First, we report the novel sparse double descent phenomenon through extensive experiments. Second, for this phenomenon, we propose a novel learning distance interpretation that the curve of $\ell_{2}$ learning distance of sparse models (from initialized parameters to final parameters) may correlate with the sparse double descent curve well and reflect generalization better than minima flatness. Third, in the context of sparse double descent, a winning ticket in the lottery ticket hypothesis surprisingly may not always win.