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结构化预测:最大边际技术

Structured Prediction: Maximum Margin Techniques
课程网址: http://videolectures.net/cmulls08_ratliff_ssmmt/  
主讲教师: Nathan Ratliff
开课单位: 卡内基梅隆大学
开课时间: 2008-02-07
课程语种: 英语
中文简介:
传统上,非平凡应用的要求与机器学习提供的预测工具之间存在不匹配。诸如自然语言处理,光学字符识别和路径规划之类的应用通常以组合推理算法来实现,例如解析算法,维特比解码和A *规划。这些推理算法必然利用问题的固有结构来有效地导航指数数目的目标元素,例如句子的所有解析树的集合,特定长度的可能单词集合,或两者之间的所有路径的集合。图中的点。另一方面,对机器学习和统计学中的监督学习技术的研究主要集中在回归和分类算法上,这些算法最多只能处理少数几个类。这些技术无法直接应用于大多数应用程序。通常,工程师需要通过引入在实践中经常强烈违反的独立性假设来精心定义可学习的子问题。然而,近年来,条件随机字段的出现,以及最大边际结构化分类,已经改变了机器学习社区对这些问题的看法。研究人员已经找到了问题的内在结构可以用来直接训练这些组合推理程序的方法。这种算法被称为结构化预测,它利用相同的隐式结构属性,使得推理算法更有效。在本演示文稿中,在高层次引入结构化预测之后,我将详细介绍结构化预测中两种被引用最多的形式之一:最大边际结构化分类。特别强调功能梯度技术,我将介绍一些解决这些问题的算法,以及它们在各种应用中的结果以及相关权衡的讨论。
课程简介: Traditionally there has been a mismatch between the requirements of nontrivial applications and the prediction tools offered by machine learning. Applications such as natural language processing, optical character recognition, and path planning are often implemented in terms combinatorial inference algorithms, such as parsing algorithms, Viterbi decoding, and A* planning. These inference algorithms necessarily utilize the inherent structure of the problem to efficiently navigate an exponential number of target elements such as the set of all parse trees for a sentence, the set of possible words of a particular length, or the set of all paths between two points in a graph. On the other hand, research into supervised learning techniques in machine learning and statistics has focused primarily on regression and classification algorithms which at best handle only a handful of classes. These techniques cannot be applied directly to most applications. Typically, engineers are required to meticulously define learnable subproblems by inducing independence assumptions which are often strongly violated in practice. In recent years, however, the advent of conditional random fields, and then maximum margin structured classification, has changed the way the machine learning community views these problems. Researchers have found ways in which the inherent structure in the problems can be used to directly train these combinatorial inference procedures. Dubbed structured prediction, this class of algorithms utilizes the same implicit structural properties that make the inference algorithms efficient. In this presentation, after introducing structured prediction at a high level, I will cover in detail one of the two most cited formalisms of structured prediction: maximum margin structured classification. With a particular emphasis placed on functional gradient techniques, I will present a number of algorithms for solving these problems along with their results on various applications and a discussion of relative trade-offs.
关 键 词: 机器学习; 监督学习技术; 最大边际结构化分类
课程来源: 视频讲座网
最后编审: 2020-06-22:chenxin
阅读次数: 124