语言模型记忆能力弱,新架构通过双目标训练实现高效存储与读取。
Language Model Memory and Memory Models for Language
- 用自编码器思路构建可逆记忆存储,替代传统token序列
- 联合训练使嵌入包含丰富信息,支持任意访问和解码
- 适合需高效存取长文本的场景,如对话系统、知识库
机器学习模型在隐藏层向量中存储输入信息的能力,类似人类记忆,但尚未被充分理解。我们发现,无论数据规模或计算资源如何,语言模型的嵌入通常仅携带少量输入信息。相比之下,为重建输入而训练的自编码器嵌入可实现近乎完美的记忆。用记忆嵌入替代词元序列能显著提升计算效率,由此提出一种可并行处理的编码器-解码器记忆模型架构。因果训练下的模型生成信息贫乏的嵌入,无法任意访问;但结合因果目标与信息保留目标后,模型学会形成并解码富含信息的记忆。通过冻结高保真编码器并采用课程学习策略——先训练解码器处理记忆,再加入下一词预测任务,可进一步简化训练过程。我们认为,仅靠下一词预测训练难以实现准确记忆,因其目标不可逆,因此对于未完整暴露输入的模型,应使用联合目标函数。
原文摘要 · Abstract (English)
The ability of machine learning models to store input information in hidden layer vector embeddings, analogous to the concept of `memory', is widely employed but not well characterized. We find that language model embeddings typically contain relatively little input information regardless of data and compute scale during training. In contrast, embeddings from autoencoders trained for input regeneration are capable of nearly perfect memory formation. The substitution of memory embeddings for token sequences leads to substantial computational efficiencies, motivating the introduction of a parallelizable encoder-decoder memory model architecture. Upon causal training these models contain information-poor embeddings incapable of arbitrary information access, but by combining causal and information retention objective functions they learn to form and decode information-rich memories. Training can be further streamlined by freezing a high fidelity encoder followed by a curriculum training approach where decoders first learn to process memories and then learn to additionally predict next tokens. We introduce the perspective that next token prediction training alone is poorly suited for accurate memory formation as the objective itself is non-invertible, motivating the use of combined objective functions for models where the entire input is not exposed.
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