  The large scale of pre-trained language models poses a challenge for their
deployment on various devices, with a growing emphasis on methods to compress
these models, particularly knowledge distillation. However, current knowledge
distillation methods rely on the model's intermediate layer features and the
golden labels (also called hard labels), which usually require aligned model
architecture and enough labeled data respectively. Moreover, the parameters of
vocabulary are usually neglected in existing methods. To address these
problems, we propose a general language model distillation (GLMD) method that
performs two-stage word prediction distillation and vocabulary compression,
which is simple and surprisingly shows extremely strong performance.
Specifically, GLMD supports more general application scenarios by eliminating
the constraints of dimension and structure between models and the need for
labeled datasets through the absence of intermediate layers and golden labels.
Meanwhile, based on the long-tailed distribution of word frequencies in the
data, GLMD designs a strategy of vocabulary compression through decreasing
vocabulary size instead of dimensionality. Experimental results show that our
method outperforms 25 state-of-the-art methods on the SuperGLUE benchmark,
achieving an average score that surpasses the best method by 3%.
