Event-based Program Analysis with DeWiz

Due to the increased complexity of parallel and distributed programs, debugging of them is considered to be the most difficult and time consuming part of the software lifecycle. Tool support is hence a crucial necessity to hide complexity from the user. However, most existing tools seem inadequate as soon as the program under consideration exploits more than a few processors over a long execution time. This problem is addressed by the novel debugging tool DeWiz (Debugging Wizard), whose focus lies on scalability. DeWiz has a modular, scalable architecture, and uses the event graph model as a representation of the investigated program. DeWiz provides a set of modules, which can be combined to generate, analyze, and visualize event graph data. Within this processing pipeline the toolset tries to extract useful information, which is presented to the user at an arbitrary level of abstraction. Additionally, DeWiz is a framework, which can be used to easily implement arbitrary user-defined modules.Comment: In M. Ronsse, K. De Bosschere (eds), proceedings of the Fifth International Workshop on Automated Debugging (AADEBUG 2003), September 2003, Ghent. cs.SE/030902

Design and Evaluation of Scalable Representations of Communication in Gantt Charts for Large-scale Execution Traces

Gantt charts are frequently used to explore execution traces of large-scale parallel programs found in high-performance computing (HPC). In these visualizations, each parallel processor is assigned a row showing the computation state of a processor at a particular time. Lines are drawn between rows to show communication between these processors. When drawn to align equivalent calls across rows, structures can emerge reflecting communication patterns employed by the executing code. However, though these structures have the same definition at any scale, they are obscured by the density of rendered lines when displaying more than a few hundred processors. A more scalable metaphor is necessary to aid HPC experts in understanding communication in large-scale traces. To address this issue, we first conduct an exploratory study to identify what visual features are critical for determining similarity between structures shown at different scales. Based on these findings, we design a set of glyphs for displaying these structures in dense charts. We then conduct a pre-registered user study evaluating how well people interpret communication using our new representation versus their base depictions in large-scale Gantt charts. Through our evaluation, we find that our representation enables users to more accurately identify communication patterns compared to full renderings of dense charts. We discuss the results of our evaluation and findings regarding the design of metaphors for extensible structures

AADEBUG2003 237 Event-based Program Analysis with DeWiz

Due to the increased complexity of parallel and distributed programs, debugging of them is considered to be the most difficult and time consuming part of the software lifecycle. Tool support is hence a crucial necessity to hide complexity from the user. However, most existing tools seem inadequate as soon as the program under consideration exploits more than a few processors over a long execution time. This problem is addressed by the novel debugging tool DeWiz (Debugging Wizard), whose focus lies on scalability. DeWiz has a modular, scalable architecture, and uses the event graph model as a representation of the investigated program. DeWiz provides a set of modules, which can be combined to generate, analyze, and visualize event graph data. Within this processing pipeline the toolset tries to extract useful information, which is presented to the user at an arbitrary level of abstraction. Additionally, DeWiz is a framework, which can be used to easily implement arbitrary user-defined modules. KEYWORDS: