CAREER: New Approaches for Ranking in Machine Learning

在许多行业中，决策都是基于大量的数据，其中可能的行动的排序列表决定了有限的资源将如何使用。在过去的十年里，用于排名的机器学习算法被设计用来解决优先级问题。这些算法根据具有某一属性的概率对一组对象进行排序；例如，我们可以根据一组井盖明年着火的概率对它们进行排序。然而，目前的算法是近似地而不是精确地解决排序问题，这些近似算法可能很慢；此外，它们没有考虑到许多特定于应用程序的问题。该项目的目标包括：I)通过开发基于混合整数优化技术的算法技术工具箱，找到排序问题的精确解。II)通过展示排序问题与更简单的分类问题的基本等价性来更快地找到解决方案，从而可以更快地解决一个数量级的问题。III)为新的结构化问题开发框架。第一个框架涉及对具有与能量域相关的图结构的问题进行排序。第二个框架处理由推荐系统引起的顺序预测问题，其应用也在医学领域。通过与工业界的合作，所提出的方法被应用于几个不同的领域，包括预防纽约市电网的严重事件（火灾和爆炸）。

In numerous industries, decisions are based on large amounts of data, where a ranked list of possible actions determines how limited resources will be spent. Over the last decade, machine learning algorithms for ranking have been designed to address prioritization problems. These algorithms rank a set of objects according to the probability to possess a certain attribute; for example, we might rank a set of manholes in order of their probability to catch fire next year. However, current algorithms solve ranking problems approximately rather than exactly, and these approximate algorithms can be slow; furthermore they do not take into account many application-specific problems.The goals of this project include: I) Finding exact solutions to ranking problems by developing a toolbox of algorithmic techniques based on mixed-integer optimization technology. II) Finding solutions faster by showing a fundamental equivalence of ranking problems to easier classification problems that can be solved an order of magnitude faster. III) Developing frameworks for new structured problems. The first framework pertains to ranking problems that have a graph structure that are relevant to the energy domain. The second framework handles a sequential prediction problem arising from recommender systems, with applications also in the medical domain.Through collaboration with industry, the proposed methods are being applied in several different areas, including the prevention of serious events (fires and explosions) on NYC's electrical grid.