Tuning the Tuner: Introducing Hyperparameter Optimization for Auto-Tuning

Abstract--Automatic performance tuning (auto-tuning) is widely used to optimize performance-critical applications across many scientific domains by finding the best program variant among many choices. Efficient optimization algorithms are crucial for navigating the vast and complex search spaces in auto-tuning. As is well known in the context of machine learning and similar fields, hyperparameters critically shape optimization algorithm efficiency. Y et for auto-tuning frameworks, these hyperparameters are almost never tuned, and their potential performance impact has not been studied. We present a novel method for general hyperparameter tuning of optimization algorithms for auto-tuning, thus "tuning the tuner". In particular, we propose a robust statistical method for evaluating hyperparameter performance across search spaces, publish a F AIR data set and software for reproducibility, and present a simulation mode that replays previously recorded tuning data, lowering the costs of hyperparameter tuning by two orders of magnitude. We show that even limited hyperparam-eter tuning can improve auto-tuner performance by 94.8% on average, and establish that the hyperparameters themselves can be optimized efficiently with meta-strategies (with an average improvement of 204.7%), demonstrating the often overlooked hyperparameter tuning as a powerful technique for advancing auto-tuning research and practice. UTOMA TIC performance tuning, or auto-tuning, is a widely established method for optimizing the performance of applications in many scientific domains, including radio astronomy [1]-[4], image processing [5]-[7], fluid dynamics [8]-[10], and climate modeling [11]-[13]. Auto-tuning automates the process of exploring the myriad of implementation choices that arise in performance optimization, such as the number of threads, tile sizes used in loop blocking, and other code optimization parameters [14]. At the heart of the auto-tuning method is a search space of functionally-equivalent code variants that is explored by an optimization algorithm.