University of Minnesota
Software Engineering Center

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Wei-Ngan Chin

Recent Publications

FixBag: A Fixpoint Calculator for Quantified Bag Constraints

Abstract interpretation techniques have played a major role in advancing the state-of-the-art in program analysis. Traditionally, stand- alone tools for these techniques have been developed for the numerical domains which may be sucient for lower levels of program correctness. To analyze a wider range of programs, we have developed a tool to compute symbolic xpoints for quantied bag domain. This domain is useful for programs that deal with collections of values. Our tool is able to derive both loop invariants and method pre/post conditions via fixpoint

Test Case Generation for Adequacy of Floating-point to Fixed-point Conversion

Porting an application written for personal computer to embedded devices requires conversion of floating-point numbers and operations into fixed-point ones. Testing the conversion hence requires the latter be as close as possible to the former. The closeness is orthogonal to code coverage and requires different strategies to generate a test suite that reveals the gap between the two functions. We introduce a new test adequacy criterion and propose several metrics to quantify the closeness of two functions.

A Fast Algorithm to Compute Heap Memory Bounds of Java Card Applets

In this paper, we present an approach to find upper bounds of heap space for Java Card applets. Our method first transforms an input bytecode stream into a control flow graph (CFG), and then collapses cycles of the CFG to produce a directed acyclic graph (DAG). Based on the DAG, we propose a linear-time algorithm to solve the problem of finding the single-source largest path in it. We also have implemented a prototype tool, tested it on several sample applications, and then compared the bounds found by our tool with the actual heap bounds of the programs.