Parallel sorting by regular sampling

ABSTRACT A new parallel sorting algorithm suitable for MIMD multiprocessors is presented. The algorithm reduces memory and bus contention, which many parallel sorting algorithms suffer from, by using a regular sampling of the data to ensure good pivot selection. For n data elements to be sorted and p processors, when n ≥ p 3 the algorithm is shown to be asymptotically optimal. In theory, the algorithm is within a factor of two of achieving ideal load balancing. In practice, there is almost perfect partitioning of work. On a variety of shared and distributed memory machines, the algorithm achieves better than half-linear speedups. -4

Interactive Story Writing in the Classroom: Using Computer Games

Computer games offer a new medium for creative writing – immersive stories where the "reader" is an active participant in the story. These stories are rich in visual and audio texture. Decisions made by the reader influence how the story unfolds (possibly even changing the outcome). In contrast to traditional pen-and-paper story writing, where the author is expected to specify everything textually, in interactive stories the "writer" uses computer tools to create visual representations of a virtual world. Vibrant colors and visual objects replace textual adjectives and vivid descriptions. Some commercial games, such as BioWare’s role-playing game Neverwinter Nights [1], provide a toolset that allows a story composer to "write" an interactive story. BioWare’s Aurora toolset has the capability to create story backdrops and scenery, and to populate the scenes with characters and supporting props. Their scripting language, NWScript, is used by the writer to specify plot components, character/prop behaviors, and their interactions. Scripting languages attempt to lessen the programming burden by presenting the user with a simplified specification language – but it is still too close to computer programming. Programming/writing interactive games with current tools is slow, cumbersome, and fraught with error. This paper discusses ScriptEase, a high-level tool for writing interactive stories that frees the author from doing explicit computer programming. To validate its ease of use for non-programmers, we describe the first time it has been used in the classroom (a Grade 10 English class). In this pilot, the students learned to use the Neverwinter Nights and ScriptEase toolsets to write interactive stories. ScriptEase By computer game standards, NWScript is a state-of-the-art scripting language, allowing the user the ability to create rich worlds and complex characters. However, the scripting language is difficult for non-programmers to learn. It closely resembles the C programming language, requiring the user to understand concepts such as functions, types, and data, as well as a large library of useful routines. This is a serious impediment to making the story creation capabilities accessible to a non-technical audience. ScriptEase is a scripting tool developed at the University of Alberta [2] that generates NWScript for Neverwinter Nights. The program provides menu-driven, textual interface that is used to specify the story. From the user specifications, the tool automatically generates the appropriate NWScript code to perform the desired actions. Writing stories in ScriptEase is accomplished using patterns. The user specifies a pattern and then customizes it to suit their needs. For example, a frequently occurring pattern in fantasy games is to open a chest and have something happen. The user selects this pattern and then sees a series of dialogue boxes that allow him/her to specify attributes for the chest. The storywriter can select a visual effect that occurs when the chest is opened and any other actions that are appropriate to the plot (a magical spell that is cast on the player’s character, a statue that animates, teleporting the player’s character to another location, etc.). A story is written by composing and customizing patterns to specify the plot, character and prop interactions, character behavior, and conversations. Classroom Pilot Working collaboratively with a high school English teacher and a high school student, a series of tutorials were created (for the tools Neverwinter Nights, Aurora, and ScriptEase) [3]. The high school teacher developed, and the high school student tested, an interactive story writing assignment targeted for High School English students. The interactive writing assignment was used as part of the curriculum in a Grade 10 English class, and administered over a two-week period in November 2004. It consisted of two components: 1. The students were taken on a field trip to the University of Alberta for the tutorials (because of the availability of computing equipment). At the end of the trip, students were ready to write their stories. 2. Three one-hour English classes were completed in the high school computer lab, allowing the students to work on their stories. Extra computer hours were made available for those who needed it. Twenty-one students completed the assignment. At the time of this writing, the assignments are currently being graded by the teacher. The conference presentation will discuss the insights gained from this classroom experience. This initial pilot has been tremendously valuable for giving feedback on the use of interactive storytelling in general, the computer tools in particular, and ways to improve the tutorials, the student computing environment, and the scope of the assignment. The initial experience was very positive for all parties. In particular, the teacher conducted a student survey after the assignment was completed and reported a very high level of satisfaction from the respondents. Future Work An experimental study using ScriptEase is planned in March/April using another English class as the target population. At the time of this writing, we are in the final stages of getting ethics approval to gather data on the students and their performance. Data will be used to identify any correlations between student abilities (e.g. problem solving skills) and background (e.g. computer experience), and how well they do on the assignment. Further, we hypothesize that some students who have difficulty expressing their creativity in words using traditional technologies may have no such limitations using interactive story writing technology. On the other hand, there may be other students who excel at traditional writing, but that do not have sufficiently developed logical thinking skills to design and create an interactive non-linear story. The development of interactive story writing technology is still in its early stages. Our work is intended to make this technology available to non-programmers, demonstrate its pedagogical value in the classroom, and work towards popularizing this medium as a new form of creative literature. References 1. BioWare Corp., http://www.bioware.com. 2. "ScriptEase: Generative Design Patterns for Computer Role-Playing Games", M. McNaughton, M. Cutumisu, D. Szafron, J. Schaeffer, J. Redford and D. Parker, Automated Software Engineering, 2004, pp. 88-99. 3. Tutorials and assignment available at http://www.cs.ualberta.ca/~script/scripteasenwn.html

Best-First and Depth-First Minimax Search in practice

Abstract Most practitioners use a variant of the Alpha-Beta algorithm, a simple depth-first procedure, for searching minimax trees. SSS*, with its best-first search strategy, reportedly offers the potential for more efficient search. However, the complex formulation of the algorithm and its alleged excessive memory requirements preclude its use in practice. For two decades, the search efficiency of "smart" best-first SSS* has cast doubt on the effectiveness of "dumb" depth-first Alpha-Beta

Nectar Yeasts in the Tall Larkspur Delphinium barbeyi (Ranunculaceae) and Effects on Components of Pollinator Foraging Behavior

Microorganisms frequently colonize the nectar of angiosperm species. Though capable of altering a suite of traits important for pollinator attraction, few studies exist that test the degree to which they mediate pollinator foraging behavior. The objective of our study was to fill this gap by assessing the abundance and diversity of yeasts associated with the perennial larkspur Delphinium barbeyi (Ranunculaceae) and testing whether their presence affected components of pollinator foraging behavior. Yeasts frequently colonized D. barbeyi nectar, populating 54–77% of flowers examined depending on site. Though common, the yeast community was species-poor, represented by a single species, Metschnikowia reukaufii. Female-phase flowers of D. barbeyi were more likely to have higher densities of yeasts in comparison to male-phase flowers. Pollinators were likely vectors of yeasts, as virgin (unvisited) flowers rarely contained yeasts compared to flowers open to pollinator visitation, which were frequently colonized. Finally, pollinators responded positively to the presence of yeasts. Bombus foragers both visited and probed more flowers inoculated with yeasts in comparison to uninoculated controls. Taken together, our results suggest that variation in the occurrence and density of nectar-inhabiting yeasts have the potential to alter components of pollinator foraging behavior linked to pollen transfer and plant fitness

Poker as a testbed for machine intelligence research

ABSTRACT For years, games researchers have used chess, checkers and other board games as a testbed for machine intelligence research. The success of world-championship-caliber programs for these games has resulted in a number of interesting games being overlooked. Specifically, we show that poker can serve as a better testbed for machine intelligence research related to decision making problems. Poker is a game of imperfect knowledge, where multiple competing agents must deal with risk management, agent modeling, unreliable information and deception, much like decision-making applications in the real world. The heuristic search and evaluation methods successfully employed in chess are not helpful here. This paper outlines the difficulty of playing strong poker, and describes our first steps towards building a world-class poker-playing program

Dual search in permutation state spaces

Abstract Geometrical symmetries are commonly exploited to improve the efficiency of search algorithms. We introduce a new logical symmetry in permutation state spaces which we call duality. We show that each state has a dual state. Both states share important attributes and these properties can be used to improve search efficiency. We also present a new search algorithm, dual search, which switches between the original state and the dual state when it seems likely that the switch will improve the chances of a cutoff. The decision of when to switch is very important and several policies for doing this are investigated. Experimental results show significant improvements for a number of applications