Software Visualization

Visualization “A picture is worth 1000 words” Effective visualization can help with the understanding of complex structures The key word is “effective” 2/4/2019 COSC6431

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2/4/2019 COSC6431

Key questions What views are useful? What technique to use? Low-level or high-level Kind of information displayed (procedure calls, data flow, control flow, inheritance) What technique to use? Automatic graph layout Animation What part of the information should be elided? 2/4/2019 COSC6431

Low-level visualizations Execution of algorithms can be visualized to help with their understanding Classic example: “Sorting out Sorting” Many tools have been developed to do this automatically 2/4/2019 COSC6431

Parallel Quicksort visualization The left view shows the values being sorted (color indicates thread) and the right view shows a history of the swaps made in the program. 2/4/2019 COSC6431

Automatic graph layout Given a graph, what is its most understandable layout? Understandability usually refers to number of edge crossings A tough problem in the general case Minimizing edge crossings for a bipartite graph with one side fixed is NP-hard 2/4/2019 COSC6431

Heuristics - Sugiyama In software systems, one often deals with layered graphs Sugiyama developed a widely used algorithm for layout of layered graphs Main idea: Minimize edge crossings by having edges be as vertical as possible Abscissa of each vertex is the average of the abscissas of its neighbours 2/4/2019 COSC6431

Sugiyama example 2/4/2019 COSC6431

Heuristics – Spring Layout Attaches forces between the nodes of a graph Connected nodes are attracted to each other, otherwise they are pushed apart Converges to a stable position Of dubious value for systems with many cycles (as most software systems are) 2/4/2019 COSC6431

Spring Layout example 2/4/2019 COSC6431

Graphviz Set of graph drawing tools from AT&T Supports both Sugiyama and Spring layout Has been used in a number of different settings Receives textual input and transforms it into graphs Bunch can produce output that Graphviz can visualize 2/4/2019 COSC6431

Data structures 2/4/2019 COSC6431

Automata 2/4/2019 COSC6431

Program profile 2/4/2019 COSC6431

Module dependencies 2/4/2019 COSC6431

Rigi Interactive, visual tool designed to help understand and re-document software Includes parsers for C, C++, and COBOL Incorporates selection, filtering, and editing operations Uses simple file format to represent graphs (RSF) 2/4/2019 COSC6431

SHriMP Views Simple Hierarchical Multi-Perspective Originally developed for program understanding Can be used for other knowledge bases as well Usual problem: How does it scale up? 2/4/2019 COSC6431

3D Visualizations A number of papers present attempts to visualize software structures in 3D While interesting, it is doubtful that these approaches can be useful (see aside on the course webpage) Some examples…. 2/4/2019 COSC6431

Metaballs 2/4/2019 COSC6431

Cone trees 2/4/2019 COSC6431

World cities 2/4/2019 COSC6431