Method for use by computing facility to determine accuracy of computer calculations is presented. Primary goals of error analysis program are described. Program is designed for both FORTRAN 4 and ASSEMBLER for use with IBM 360 computer

Cole, I.

English

NASA Technical Reports Server

October 1972	 B72-10600 
NASA TECH BRIEF 
Goddard Space Flight Center 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Significance Arithmetic Experimental Package (SIGPAC) 
The problem: 
To provide a fully mechanistic "numerical procedure 
debugging" tool for users of conventional procedural 
programming languages (initially, Standard FORTRAN). 
This method would test actual error propagation in 
numerical calculations. 
The solution: 
A software package was developed to solve the 
problem stated above. 
How it's done: 
SIGPAC consists, in effect, of a compiler from 
FORTRAN source language into an artificial object 
language in which arithmetic operations produce, in 
addition to numerical. results, a measure of the current 
significance of each result operand. 
The purpose of SIGPAC is to provide to the scientific 
and engineering users of the IBM-360/95 computing 
facility a convenient, effective, and quite general means 
for testing and indicating the accuracy of computer 
calculations. 
This work has two primary goals. 
(a) To permit the testing and localizing of weaknesses 
within numerical procedures for abnormal error
propagation from generated (primary truncation) 
errors. 
(b) To provide an objective basis for determining when 
single precision gives adequate significance or 
when double precision should be used. 
Notes: 
1. This program is programmed in both FORTRAN IV 
(7217o) and ASSEMBLER (28%) languages to be 
utilized by the IBM-360/95 computer. 
2. Inquiries concerning this program should be directed 
to:
COSMIC 
112 Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: GSC-1 1499
Source: Isabella Cole
Goddard Space Flight Center and

Computation Planning, Inc.

under contract to

Goddard Space Flight Center

(GSC-1 1499) 
Category 09 
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Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
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Significance arithmetic experimental package (SIGPAC)

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