Global optimization based on active preference learning with radial basis functions

AbstractThis paper proposes a method for solving optimization problems in which the decision-maker cannot evaluate the objective function, but rather can only express apreferencesuch as "this is better than that" between two candidate decision vectors. The algorithm described in this paper aims at reaching the global optimizer by iteratively proposing the decision maker a new comparison to make, based on actively learning a surrogate of the latent (unknown and perhaps unquantifiable) objective function from past sampled decision vectors and pairwise preferences. A radial-basis function surrogate is fit via linear or quadratic programming, satisfying if possible the preferences expressed by the decision maker on existing samples. The surrogate is used to propose a new sample of the decision vector for comparison with the current best candidate based on two possible criteria: minimize a combination of the surrogate and an inverse weighting distance function to balance between exploitation of the surrogate and exploration of the decision space, or maximize a function related to the probability that the new candidate will be preferred. Compared to active preference learning based on Bayesian optimization, we show that our approach is competitive in that, within the same number of comparisons, it usually approaches the global optimum more closely and is computationally lighter. Applications of the proposed algorithm to solve a set of benchmark global optimization problems, for multi-objective optimization, and for optimal tuning of a cost-sensitive neural network classifier for object recognition from images are described in the paper. MATLAB and a Python implementations of the algorithms described in the paper are available athttp://cse.lab.imtlucca.it/~bemporad/glis

Application of data mining in scheduling of single machine system

The rapidly growing field of data mining has the potential of improving performance of existing scheduling systems. Such systems generate large amounts of data, which is often not utilized to its potential. The problem is whether it is possible to discover the implicit knowledge behind scheduling practice and then, with this knowledge, we could improve current scheduling practice. In this dissertation, we propose a novel methodology for generating scheduling rules using a data-driven approach. We show how to use data mining to discover previously unknown dispatching rules by applying the learning algorithms directly to production data. We also consider how by using this new approach unexpected knowledge and insights can be obtained, in a manner that would not be possible if an explicit model of the system or the basic scheduling rules had to be obtained beforehand. However, direct data mining of production data can at least mimic scheduling practices. The problem is whether scheduling practice could be improved with the knowledge discovered by data mining. We propose to combine data mining with optimization for effective production. In this approach, we use a genetic algorithm to find a heuristic solution to the optimal instances selection problem, and then induce a decision tree from this subset of instances. The optimal instance selection can be viewed as determining the best practices from what has been done in the past, and the data mining can then learn new dispatching rules from those best practices

Towards building a review recommendation system that trains novices by leveraging the actions of experts

Online reviews increase consumer visits, increase the time spent on the website, and create a sense of community among the frequent shoppers. Because of the importance of online reviews, online retailers such as Amazon.com and eOpinions provide detailed guidelines for writing reviews. However, though these guidelines provide instructions on how to write reviews, reviewers are not provided instructions for writing product-specific reviews. As a result, poorly-written reviews are abound and a customer may need to scroll through a large number of reviews, which could be up to 6000 pixels down from the top of the page, in order to find helpful information about a product (Porter, 2010). Thus, there is a need to train reviewers to write better reviews, which could in turn better serve customers, vendors, and online e-stores. In this Thesis, we propose a review recommendation framework to train reviewers to better write about their experiences with a product by leveraging the behaviors of expert reviewers who are good at writing helpful reviews. First, we use clustering to model reviewers into different classes that reflect different skill levels to write a quality review such as expert, novice, etc. Through temporal analysis of reviewer behavior, we have found that reviewers evolve over time, with their reviews becoming better or worse in quality and more or less in quantity. We also investigate how reviews are valued differently across different product categories. Through machine learning-based classification techniques, we have found that, for products associated with prevention consumption goal, longer reviews are perceived to be more helpful; and, for products associated with promotion consumption goal, positive reviews are more helpful than negative ones. In this Thesis, our proposed review recommendation framework is aimed to help a novice or conscientious reviewer become an expert reviewer. Our assumption is that a reviewer will reach the highest level of expertise by learning from the experiences of his or her closest experts who have a similar evolutionary pattern to that of the reviewer who is being trained. In order to provide assistance with intermediate steps for the reviewer to grow from his or her current state to the highest level of expertise, we want to recommend the positive actions—that are not too far out of reach of the reviewer—and discourage the negative actions—that are within reach of the reviewer—of the reviewer’s closest experts. Recommendations are personalized to fit the expertise level of reviewers, their evolution trend, and product category. Using the proposed review recommendation system framework we have found that for a random reviewer, at least 80% of the reviews posted by closest experts were of higher quality than that of the novice reviewer. This is verified in a dataset of 2.3 million reviewers, whose reviews cover products from nine different product categories such as Books, Electronics, Cellphones and accessories, Grocery and gourmet food, Office product, Health and personal care, Baby, Beauty, and Pet supplies. Advisor: Leen-Kiat So

Active preference learning for personalized calendar scheduling assistance

We present PLIANT, a learning system that supports adaptive assistance in an open calendaring system. PLIANT learns user preferences from the feedback that naturally occurs during interactive scheduling. It contributes a novel application of active learning in a domain where the choice of candidate schedules to present to the user must balance usefulness to the learning module with immediate benefit to the user. Our experimental results provide evidence of PLIANT’s ability to learn user preferences under various conditions and reveal the tradeoffs made by the different active learning selection strategies

A conversation centric approach to understanding and supporting the coordination of social group-activities

Despite the widespread and large variety of communication tools available to us such as, text messaging, Skype, email, twitter, Facebook, instant messaging, GroupMe, WhatsApp, Snapchat, etc., many people still routinely find coordinating activities with our friends to be a very frustrating experience. Everyone, has at least once, encountered the difficulties involved with deciding what to do as a group. Some friends may be busy, others may have already seen the movie that the others want to see, and some do not like Mexican food. It is a challenge everyone has faced and continue to face. This is a result of system designers and researchers primarily focusing on understanding and supporting workplace coordination. This workplace bias has led to an assumption that the same technologies employed to facilitate workplace coordination can easily transfer to social coordination. This has created a divergence between how people actually communicate and coordinate for social reasons versus how the systems and technologies developed to support such coordination and communication are designed. As a result, researchers and designers are faced with dearth of knowledge about how to design and research systems that support people engaging in coordination and communication for more social reasons. This dissertation moves beyond previous work, both academic and commercial, which has either focused on providing structured and process oriented communication and coordination support or on the creation of yet another text chat. This research focuses on a narrower aspect of social communication and coordination, specifically, the problem of social group-activity coordination. Generally, this is the stuff people do to coordinate going out to dinner or the movies with a group of friends. This area has been under researched and as personal experience informs, poorly supported. This dissertation contains four main contributions. First, a diary study of 37 young adults aged 18 to 28 investigated the current social group-activity coordination practices resulting in an expansion of the knowledge about how social groups coordinate social group-activities and what technologies people use and why. Second, via iterative design and testing following a research through design methodology the design space for social group-activity coordination is explored over multiple design iterations. This results in the design and instantiation of a social group-activity coordination support tool improving understanding of the design requirements of tools that support social group-activity coordination. Third, a quantitative survey which confirmed many of the findings discovered during the dairy study. Fourth, the tool is evaluated in a laboratory study with 84 participants during 21 sessions. This study finds that using the conversation centric design perspective presented in this dissertation it is possible to reduce information overload and support consensus building. Also, the features provided are overwhelmingly desired with 91.4% of the participants desiring the ability and interface to make suggestions about important activity details (vs open chat) and two-thirds of the participants reporting they would prefer to use this tool over text messaging. The combination of all these different investigations into social group-activity coordination extends the knowledge about how to improve the support of social group-activity coordination and move beyond the process and systems oriented perspectives and towards conversation centric designs