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arXiv 2101.09313cs.CLcs.LG
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$k$ -用于序列预测的基于邻居的课程采样

$k$-Neighbor Based Curriculum Sampling for Sequence Prediction

University of Liverpool(利物浦大学)

James O' Neill, Danushka Bollegala

摘要:

语言模型中的多步预测是具有挑战性的,由于训练和测试时间过程之间的差异。在测试时,序列预测器需要以过去的预测作为输入来进行预测,而不是在训练期间提供的过去的目标。这种差异称为暴露偏差,可能导致测试时生成的序列中出现复合错误。为了提高神经语言模型的泛化能力并解决复合错误,我们提出了\textit{Nearest-Neighbor Replacement Sampling} -一种基于课程学习的方法,该方法将最初确定的教师政策逐渐改变为随机政策。在给定的时间步长处的标记被替换为过去目标的采样的最近邻居,其截断概率与原始单词和其顶部$k$最相似单词之间的余弦相似度成比例。这允许学习者在教师提供的当前策略次优或难以学习时探索替代方案。所提出的方法是直接的,在线的,需要很少的额外的内存要求。我们报告我们的研究结果,两个语言建模基准,并发现所提出的方法进一步提高性能时,与预定的采样。

英文摘要:

Multi-step ahead prediction in language models is challenging due to the discrepancy between training and test time processes. At test time, a sequence predictor is required to make predictions given past predictions as the input, instead of the past targets that are provided during training. This difference, known as exposure bias, can lead to the compounding of errors along a generated sequence at test time. To improve generalization in neural language models and address compounding errors, we propose \textit{Nearest-Neighbor Replacement Sampling} -- a curriculum learning-based method that gradually changes an initially deterministic teacher policy to a stochastic policy. A token at a given time-step is replaced with a sampled nearest neighbor of the past target with a truncated probability proportional to the cosine similarity between the original word and its top $k$ most similar words. This allows the learner to explore alternatives when the current policy provided by the teacher is sub-optimal or difficult to learn from. The proposed method is straightforward, online and requires little additional memory requirements. We report our findings on two language modelling benchmarks and find that the proposed method further improves performance when used in conjunction with scheduled sampling.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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