Visualization of computer programs, particularly parallel programs, promises to help programmers better understand, develop, and debug their code, especially if the visualizations are relatively easy to create. We have developed a visualization methodology being used as a component in a comprehensive parallel program visualization system. The focus of the system is on application-specific user-tailored program views. An application-specific visualization of a parallel program presents the inherent application domain, semantics, and data being manipulated by the program in a manner natural to one's understanding of the program. In this paper we discuss why application-specific views are necessary for program debugging, and we list several requirements and challenges that a system for applicationspecific viewing should meet. The visualization methodology that we introduce includes primitives for designing smooth animation scenarios, and most importantly, for allowing designers to visuali...

Algorithm visualization (AV) technology graphically illustrates how algorithms work. Despite the intuitive appeal of the technology, it has failed to catch on in mainstream computer science education. Some have attributed this failure to the mixed results of experimental studies designed to substantiate AV technology's educational effectiveness. However, while several integrative reviews of AV technology have appeared, none has focused specifically on the software's effectiveness by analyzing this body of experimental studies as a whole. In order to better understand the effectiveness of AV technology, we present a systematic metastudy of 24 experimental studies. We pursue two separate analyses: an analysis of independent variables, in which we tie each study to a particular guiding learning theory in an attempt to determine which guiding theory has had the most predictive success; and an analysis of dependent variables, which enables us to determine which measurement techniques have been most sensitive to the learning benefits of AV technology. Our most significant finding is that how students use AV technology has a greater impact on effectiveness than what AV technology shows them. Based on our findings, we formulate an agenda for future research into AV effectiveness.

User interfaces are often based on static presentations, a model ill suited for conveying change. Consequently, events on the screen frequently startle and confuse users. Cartoon animation, in contrast, is exceedingly successful at engaging its audience; even the most bizarre events are easily comprehended. The Self user interface has served as a testbed for the application of cartoon animation techniques as a means of making the interface easier to understand and more pleasant to use. Attention to timing and transient detail allows Self objects to move solidly. Use of cartoon-style motion blur allows Self objects to move quickly and still maintain their comprehensibility. Self objects arrive and depart smoothly, without sudden materializations and disappearances, and they rise to the front of overlapping objects smoothly through the use of dissolve. Anticipating motion with a small contrary motion and pacing the middle of transitions faster than the endpoints results in smoother and c...

This paper focuses on the opportunities and costs of on-line steering as applied to a substantial parallel application. We demonstrate potential performance improvements through the use of the Falcon system, an experimental system for the on-line monitoring and steering of parallel programs. The visual presentation of program output along with animated displays of program performance information via Falcon's monitoring system enables the on-line capture, analysis, and display of program information required for program steering. Falcon also provides the mechanisms for the manipulations of program state that accomplish this online steering. 1 Interactive parallel programs Future parallel applications will run on a variety of parallel machines linked with high performance networks. The primary purpose of our research is to exploit these modern systems' capabilities to offer human-interactive interfaces that can execute simultaneously with a parallel application's computational and stor...

Adding animation to interfaces is a very difficult task with today's toolkits, even though there are many situations in which it would be useful and effective. The Amulet toolkit contains a new form of animation constraint that allows animations to be added to interfaces extremely easily without changing the logic of the application or the graphical objects themselves. An animation constraint detects changes to the value of the slot to which it is attached, and causes the slot to instead take on a series of values interpolated between the original and new values. The advantage over previous approaches is that animation constraints provide significantly better modularity and reuse. The programmer has independent control over the graphics to be animated, the start and end values of the animation, the path through value space, and the timing of the animation. Animations can be attached to any object, even existing widgets from the toolkit, and any type of value can be animated: scalars, ...

Algorithm visualization software graphically illustrates how computer algorithms work. Past experiments designed to substantiate the software's pedagogical value have yielded mixed results. A review of these studies suggests that the more actively involved learners are in the visualization process, the better they perform. Given this trend, and inspired by ethnographic fieldwork we conducted in an undergraduate algorithms course, we hypothesize that students who use simple art supplies to construct their own visualizations will learn an algorithm better than students who interact with computer-based visualizations constructed by an expert. We conducted an experiment to test this hypothesis, and found no significant differences between the two pedagogical approaches. Thus, students who use "low tech" materials to construct their own visualizations may learn algorithms just as well as students who study conventional "high tech" visualizations constructed by an expert. This result motivates a markedly different kind of algorithm visualization software: one that enables learners to construct their own "low tech" visualizations. 1.

Until now, only users of textual programming languages have enjoyed the fruits of algorithm animation. Users of visual programming languages (VPLs) have been deprived of the unique semantic insights algorithm animation offers, insights that would foster the understanding and debugging of visual programs. To begin solving this shortcoming, we have seamlessly integrated algorithm animation capabilities into Forms/3, a declarative VPL in which evaluation is the continuous maintenance of a network of one-way constraints. Our results show that a VPL that uses this constraint-based evaluation model can provide features not found in other algorithm animation systems. 1: Introduction Algorithm animation is a type of software visualization of growing importance. It is a dynamic visualization of the main abstractions of a program's underlying algorithm. The value of algorithm animation lies in its ability to portray the essence of the program's logic, avoiding the obscuring of this essence tha...

Visualizing information in user interfaces to complex, large-scale systems is difficult due to an enormous amount of dynamic data distributed across multiple displays. While graphical representation techniques can reduce some of the cognitive overhead associated with comprehension, current interfaces suffer from the over-use of such representation techniques and exceed the human’s perceptual capacity to efficiently interpret them. New display dimensions are required to support the user in information visualization. Three major issues which are problematic in complex system UI design are identified: representing the nature of change, supporting the cognitive integration of data across disparate displays, and conveying the nature of relationships between data and/ or events. Advances in technology have made animation a viable alternative to static representations. Motion holds promise as a perceptually rich and efficient display dimension but little is known about its attributes for information display. This paper proposes that motion may prove useful in visualizing complex information because of its preattentive and interpretative perceptual properties. A review of animation in current user interface and visualization design and research indicates that, while there is strong intuition about the “usefulness ” of motion to communicate, there

Abstract. Interaction and feedback are key factors supporting the learning process. Therefore many automatic assessment and feedback systems have been developed for computer science courses during the past decade. In this paper we present a new framework, TRAKLA2, for building interactive algorithm simulation exercises. Exercises constructed in TRAKLA2 are viewed as learning objects in which students manipulate conceptual visualizations of data structures in order to simulate the working of given algorithms. The framework supports randomized input values for the assignments, as well as automatic feedback and grading of students ’ simulation sequences. Moreover, it supports automatic generation of model solutions as algorithm animations and the logging of statistical data about the interaction process resulting as students solve exercises. The system has been used in two universities in Finland for several courses involving over 1000 students. Student response has been very positive. Key words: algorithms, data structures, algorithm animation, algorithm simulation, automatic assessment, computer science education. 1.

Computer science educators have traditionally used algorithm visualization (AV) software to create graphical representations of algorithms for use as visual aids in lectures, or as the basis for interactive labs. Typically, such visualizations are high fidelity in the sense that (a) they depict the target algorithm for arbitrary input, and (b) they tend to have the polished look of textbook figures. In contrast, low fidelity visualizations illustrate the target algorithm for a few, carefully chosen input data sets, and tend to have a sketched, unpolished appearance. Drawing on ethnographic field studies of a junior-level algorithms course, we motivate the use of low fidelity AV technology as the basis for an alternative learning paradigm in which students construct their own visualizations, and then present those visualizations to their instructor and peers for feedback and discussion. To explore the design space of low fidelity AV technology, we present SALSA (Spatial ALgorithmic Language for StoryboArding) and ALVIS (ALgorithm VIsualization Storyboarder), a prototype end-user language and system firmly rooted in empirical studies in which students constructed and presented visualizations made out of simple art supplies. Our prototype end-user language and system pioneer a novel technique for programming of visualizations based on spatial relations, and a novel presentation interface that supports human discussions about algorithms by enabling reverse execution and dynamic mark-up and modification. Moreover, the prototype provides an ideal foundation for what we see as the algorithms classroom of the future: the interactive "algorithms studio."