Standard compiler optimization levels, such as -O3 , which provides a fixed optimization strategy for all programs, often fail to deliver the optimal performance. Compiler auto-tuning techniques can deliver substantial speedups, but existing methods present a difficult tradeoff. While dynamic iterative approaches are effective, their requirement for repeated compilation and execution incurs high overhead, which limits their practicality. Conversely, static prediction methods offer a low-overhead alternative. However, they face a vast search space and must comprehensively learn both option-option interactions and option-program feature relationships. To overcome the challenge, we propose PredComp , a novel static framework that leverages the divide and conquer paradigm to predict desired option sets. PredComp decomposes the search space by partitioning options into distinct subspaces based on their relationships, making the prediction problem tractable. It first predicts promising option sub-sets within each subspace, focusing only on intra-subspace option interactions and their preferred program features. Then, it adopts a combination model that aggregates these top-ranked sub-sets, prioritizes inter-subspace option interactions and corresponding features to construct globally desired sets. Experiments on three widely used benchmark suites and one real-world application show that PredComp achieves average speedups of 1.1011× over -O3 with a single prediction. Notably, it achieves performance comparable to dynamic iterative methods while reducing tuning time from hours or days to seconds, thereby making static prediction a practical solution for large-scale and frequently evolving software.

Modern compilers typically provide hundreds of options to optimize program performance, but users often cannot fully leverage them due to the huge number of options. While standard optimization combinations (e.g., -O3) provide reasonable defaults, they often fail to deliver near-peak performance across diverse programs and architectures. To address this challenge, compiler auto-tuning techniques have emerged to automate the discovery of improved option combinations. Existing techniques typically focus on identifying critical options and prioritizing them during the search to improve efficiency. However, due to limited tuning iterations, the resulting data is often sparse and noisy, making it highly challenging to accurately identify critical options. As a result, these algorithms are prone to being trapped in local optima. To address this limitation, we propose GroupTuner, a group-aware auto-tuning technique that directly applies localized mutation to coherent option groups based on historically best-performing combinations, thus avoiding explicitly identifying critical options. By forgoing the need to know precisely which options are most important, GroupTuner maximizes the use of existing performance data, ensuring more targeted exploration. Extensive experiments demonstrate that GroupTuner can efficiently discover competitive option combinations, achieving an average performance improvement of 12.39% over -O3 while requiring only 77.21% of the time compared to the random search algorithm, significantly outperforming state-of-the-art methods.

Music recommendation systems aim to suggest tracks that users may enjoy. However, the accuracy of recommendation results is affected by popularity bias. Previous studies have focused on mitigating the direct effect of single-item popularity in video, news, or e-commerce recommendations, but have overlooked the multisource popularity biases in music recommendations. This article proposes a causal inference-based method to reduce the influence of both track and artist popularity. First, we construct a causal graph that encompasses users, tracks, and artists within the context of music recommendations. Next, we employ matrix factorization in conjunction with counterfactual inference theory to mitigate the popularity effects of artists and tracks, taking into account both the natural direct and indirect effects of these entities on music recommendations. Experimental results evaluated on four music recommendation datasets indicate that our method outperforms other baselines and effectively alleviates the popularity bias of both tracks and artists.