When bugs or defects are introduced into a large scale software repository, they reduce productivity. Programmers working on related areas of the code will encounter test failures, compile breakages, or other anomalous behavior. On encountering these issues, they will need to troubleshoot and determine that their changes were not the cause of the error and that another change is at fault. They must then find that change and revert it to return the repository to a healthy state. In the past, our group has identified ways to identify the root cause (or culprit) change that introduced a test failure even when the test is flaky. This paper focuses on a related issue: at what point does the Continuous Integration system have enough evidence to support automatically reverting a change? We will motivate the problem, provide several methods to address it, and empirically evaluate our solution on a large set (25,137) of real-world breaking changes that occurred at Google. SafeRevert improved recall (number of changes recommend for reversion) by 2× over the baseline method while meeting our safety criterion.

When a change introduces a bug into a large software repository, there is often a delay between when the change is committed and when bug is detected. This is true even when the bug causes an existing test to fail! These delays are caused by resource constraints which prevent the organization from running all of the tests on every change. Due to the delay, a Continuous Integration system needs to locate buggy commits. Locating them is complicated by flaky tests that pass and fail non-deterministically. The flaky tests introduce noise into the CI system requiring costly reruns to determine if a failure was caused by a bad code change or caused by non-deterministic test behavior. This paper presents an algorithm, Flake Aware Culprit Finding, that locates buggy commits more accurately than a traditional bisection search. The algorithm is based on Bayesian inference and noisy binary search, utilizing prior information about which changes are most likely to contain the bug. A large scale empirical study was conducted at Google on 13,000+ test breakages. The study evaluates the accuracy and cost of the new algorithm versus a traditional deflaked bisection search.

Media research has shown that people enjoy watching television as a part of socializing in groups. However, many constraints in daily life limit the opportunities for doing so. The Social TV project builds on the increasing integration of television and computer technology to support sociable, computer-mediated group viewing experiences. In this article, we describe the initial results from a series of studies illustrating how people interact in front of a television set. Based on these results, we propose guidelines as well as specific features to inform the design of future “social television” prototypes.

Massively multiplayer online games (MMOGs) can be fascinating laboratories to observe group dynamics online. In particular, players must form persistent associations or "guilds" to coordinate their actions and accomplish the games' toughest objectives. Managing a guild, however, is notoriously difficult and many do not survive very long. In this paper, we examine some of the factors that could explain the success or failure of a game guild based on more than a year of data collected from five World of Warcraft servers. Our focus is on structural properties of these groups, as represented by their social networks and other variables. We use this data to discuss what games can teach us about group dynamics online and, in particular, what tools and techniques could be used to better support gaming communities.

Massively multiplayer online games (MMOGs) currently represent the most widely used type of social 3D virtual worlds with millions of users worldwide. Although MMOGs take face-to-face conversation as their metaphor for user-to-user interaction, avatars currently give off much less information about what users are doing than real human bodies. Consequently, users routinely encounter slippages in coordination when engaging in joint courses of action. In this study, we analyze screen-capture video of user-to-user interaction in the game, City of Heroes, under two conditions: one with the game's standard awareness cues and the other with enhanced cues. We use conversation analysis to demonstrate interactional slippages caused by the absence of awareness cues, user practices that circumvent such limitations and ways in which enhanced cues can enable tighter coordination.

Massively Multiplayer Online Games (MMOGs) routinely attract millions of players but little empirical data is available to assess their players' social experiences. In this paper, we use longitudinal data collected directly from the game to examine play and grouping patterns in one of the largest MMOGs: World of Warcraft. Our observations show that the prevalence and extent of social activities in MMOGs might have been previously over-estimated, and that gaming communities face important challenges affecting their cohesion and eventual longevity. We discuss the implications of our findings for the design of future games and other online social spaces.