Assessing the Portability of Parameter Matrices Trained by Parameter-Efficient Finetuning Methods
This addresses the problem of reusing task-specific knowledge across models for researchers and practitioners, though it is incremental as it builds on existing PEFT methods.
The paper investigates whether task-specific modules trained via parameter-efficient finetuning (PEFT) can be transferred between models, finding in 1,440 runs that ported modules significantly outperform scratch-trained or randomly initialized alternatives, with performance varying by PEFT technique and model differences.
As the cost of training ever larger language models has grown, so has the interest in reusing previously learnt knowledge. Transfer learning methods have shown how reusing non-task-specific knowledge can help in subsequent task-specific learning. In this paper, we investigate the inverse: porting whole functional modules that encode task-specific knowledge from one model to another. We designed a study comprising 1,440 training/testing runs to test the portability of modules trained by parameter-efficient finetuning (PEFT) techniques, using sentiment analysis as an example task. We test portability in a wide range of scenarios, involving different PEFT techniques and different pretrained host models, among other dimensions. We compare the performance of ported modules with that of equivalent modules trained (i) from scratch, and (ii) from parameters sampled from the same distribution as the ported module. We find that the ported modules far outperform the two alternatives tested, but that there are interesting performance differences between the four PEFT techniques. We conclude that task-specific knowledge in the form of structurally modular sets of parameters as produced by PEFT techniques is highly portable, but that degree of success depends on type of PEFT and on differences between originating and receiving pretrained models.