Numeric issues in test software correctness

Robert G. Hayes, Raytheon Infrared Operations
Gary B. Hughes, Raytheon Infrared Operations
Phillip M. Dorin, Loyola Marymount University
Raymond J. Toal, Loyola Marymount University

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Copyright © 2002 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. The definitive version is available at http://dx.doi.org/10.1109/AUTEST.2002.1047948.

NOTE: At the time of publication, the author Gary Hughes was not yet affiliated with Cal Poly.

Abstract

Test system designers are comfortable with the concepts of precision and accuracy with regard to measurements achieved with modern instrumentation. In a well-designed test system, great care is taken to ensure accurate measurements, with rigorous attention to instrument specifications and calibration. However, measurement values are subjected to representation and manipulation as limited precision floating-point numbers by test software. This paper investigates some of the issues related to floating point representation of measurement values, as well as the consequences of algorithm selection. To illustrate, we consider the test case of standard deviation calculations as used in the testing of infrared focal plane arrays. We consider the concept of using statistically-based techniques for selection of an appropriate algorithm based on measurement values, and offer guidelines for the proper expression and manipulation of measurement values within popular test software programming frameworks.