APE: Selective Fine-tuning with Acceptance Criteria for Language Model Adaptation

Abstract

We present Adjacent Possible Exploration (APE), a selective fine-tuning method for adapting large language models that systematically explores parameter modifications while maintaining model stability. Inspired by evolutionary optimization principles, APE evaluates multiple candidate parameter updates through fine-tuning on small data subsets and accepts only those exceeding a performance threshold. Unlike standard fine-tuning that follows single gradient directions, APE implements a filtered selection process that prevents destabilizing parameter changes while enabling systematic improvement. Our method achieves 33.9\% BLEU improvement and 36.2\% perplexity reduction on news summarization tasks while using minimal computational resources. The approach provides a practical framework for controlled model adaptation that balances performance gains with representational stability.

arXiv commentWithdrawn by the author. The experiments reported in Section 3 (Table 3, Figure 2) do not implement the acceptance criterion described in Section 2, and the human evaluation in Section 3.2 is not valid. The reported results and conclusions should be disregarded