The Importance of Generation Order in Language Modeling

Abstract: Neural LLMs are a critical component of state-of-the-art systems for machine translation, summarization, audio transcription, and other tasks. These LLMs are almost universally autoregressive in nature, generating sentences one token at a time from left to right. This paper studies the influence of token generation order on model quality via a novel two-pass LLM that produces partially-filled sentence "templates" and then fills in missing tokens. We compare various strategies for structuring these two passes and observe a surprisingly large variation in model quality. We find the most effective strategy generates function words in the first pass followed by content words in the second. We believe these experimental results justify a more extensive investigation of generation order for neural LLMs.