COMBINATORIAL GEOUP TESTING ATOIfSAPPUCATIONS SERIES ON APPLIED MATHEMATICS Editor-in-Chief: Frank Hwang Associate Editors-in-Chief: Zhong-ci Shi and Kunio Tanabe Vol. 1 International Conference on Scientific Computation eds. T. Chan and Z.-C. Shi Vol. 2 Network Optimization Problems — Algorithms, Applications and Complexity eds. D.-Z. Du and P. M. Pandalos Vol. 3 Combinatorial Group Testing and Its Applications by D.-Z. Du and F. K. Hwang Vol. 4 Computation of Differential Equations and Dynamical Systems eds. K. Feng and Z.-C. Shi Vol. 5 Numerical Mathematics eds. Z.-C. Shi and T. Ushijima Series on Applied Mathematics Volume 3 Ding-Zhu Du Department of Computer Science University of Minnesota and Institute of Applied Mathematics Academia Sinica, Beijing Frank K. Hwang AT&T Bell Laboratories Murray Hill V fe World Scientific «• SSininggaappoorere • •N Neeww J Jeersrseeyy •L L ondon • Hong Kong Published by World Scientific Publishing Co. Pte. Ltd. P O Box 128, Farrer Road, Singapore 9128 USA office: Suite IB, 1060 Main Street, River Edge, NJ 07661 UK office: 73 Lynton Mead, Totteridge, London N20 8DH Library of Congress Cataloging-in-Publication Data Du, Dingzhu. Combinatorial group testing and its applications / Ding-Zhu Du, Frank K. Hwang. p. cm. — (Series on applied mathematics; vol. 3) Includes bibliographical references and index. ISBN 9810212933 1. Combinatorial group theory. I. Hwang, Frank. II. Title. III. Series: Series on applied mathematics v. 3. QA182.5.D8 1993 512'.2-dc20 93-26812 CIP Copyright © 1993 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form orby any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 27 Congress Street, Salem, MA 01970, USA. Printed in Singapore by JBW Printers & Binders Pte. Ltd. Preface Group testing has been around for fifty years. It started as an idea to do large scale blood testing economically. When such needs subsided, group testing stayed dormant for many years until it was revived with needs for new industrial testing. Later, group testing also emerged from many nontesting situations, such as experimental designs, multiaccess communication, coding theory, clone library screening, nonlinear optimization, computational complexity, etc.. With a potential world-wide outbreak of AIDS, group testing just might go the full cycle and becomes an effective tool in blood testing again. Another fertile area for application is testing zonal environmental pollution. Group testing literature can be generally divided into two types, probabilistic and combinatorial. In the former, a probability model is used to describe the distribution of defectives, and the goal is to minimize the expected number of tests. In the latter, a deterministic model is used and the goal is usually to minimize the number of tests under a worst-case scenario. While both types are important, we will focus on the second type in this book because of the different flavors for these two types of results. To find optimal algorithms for combinatorial group testing is difficult, and there are not many optimal results in the existing literature. In fact, the computational complexity of combinatorial group testing has not been determined. We suspect that the general problem is hard in some complexity class, but do not know which class. (It has been known that the problem belongs to the class PSPACE, but seems not PSPACE-complete.) The difficulty is that the input consists of two or more integers, which is too simple for complexity analysis. However, even if a proof of hardness will eventually be given, this does not spell the end of the subject, since the subject has many, many branches each posing a different set of challenging problems. This book is not only the first attempt to collect all theory and applications about combinatorial group testing in one place, but it also carries the personal perspective of the authors who have worked on this subject for a quarter of a century. We hope that this book will provide a forum and focus for further research on this subject, and also be a source for references and publications. Finally, we thank E. Barillot, A.T. Borchers, R.V. Book, G.J. Chang, F.R.K. Chung, A.G. Dyachkov, D. Kelley, K.-I Ko, M. Parnes, D. Raghavarao, M. Ruszinko, V.V. Rykov, J. Spencer, M. Sobel, U. Vaccaro, and A.C. Yao for giving us encouragements and helpful discussions at various stage of the formation of this book. Of course, the oversights and errors are our sole responsibility. v This page is intentionally left blank Contents Preface v Chapter 1 Introduction 1 1.1 The History of Group Testing 1 1.2 The Binary Tree Representation of a Group Testing Algorithm and the Information Lower Bound 5 1.3 The Structure of Group Testing 7 1.4 Number of Group Testing Algorithms 10 1.5 A Prototype Problem and Some Basic Inequalities 12 1.6 Variations of the Prototype Problem 17 References 18 Chapter 2 General Algorithms 19 2.1 Li's s-Stage Algorithm 19 2.2 Hwang's Generalized Binary Splitting Algorithm 20 2.3 The Nested Class 23 2.4 (d, n) Algorithms and Merging Algorithms 27 2.5 Some Practical Considerations 30 2.6 An Application to Clone Screenings 34 References 36 Chapter 3 Algorithms for Special Cases 38 3.1 Two Disjoint Sets Each Containing Exactly One Defective 38 3.2 An Application to Locating Electrical Shorts 43 3.3 The 2-Defective Case 48 3.4 The 3-Defective Case 53 3.5 When is Individual Testing Minimax? 56 3.6 Identifying a Single Defective with Parallel Tests 59 References 60 vii viii Contents Chapter 4 Nonadaptive Algorithms and Binary Superimposed Codes . 62 4.1 The Matrix Representation 62 4.2 Basic Relations and Bounds 63 4.3 Constant Weight Matrices and Random Codes 68 4.4 General Constructions 73 4.5 Special Constructions 78 References 87 Chapter 5 Multiaccess Channels and Extensions 91 5.1 Multiaccess Channels 92 5.2 Nonadaptive Algorithms 96 5.3 Two Variations 99 5.4 The k-Channel 101 5.5 Quantitative Channels 105 References 105 Chapter 6 Some Other Group Testing Models 107 6.1 Symmetric Group Testing 107 6.2 Some Additive Models 109 6.3 A Maximum Model 115 6.4 Some Models for d = 2 118 References 123 Chapter 7 Competitive Group Testing 126 7.1 The First Competitiveness 126 7.2 Bisecting 128 7.3 Doubling 132 7.4 Jumping 134 7.5 The Second Competitiveness 138 7.6 Digging 140 7.7 Tight Bound 143 References 148 Chapter 8 Unreliable Tests 149 8.1 Ulam's Problem 149 8.2 Geperal Lower and Upper Bounds 155 8.3 Linearly Bounded Lies (1) 160 Contents ix 8.4 The Chip Game 164 8.5 Linearly Bounded Lies (2) 168 8.6 Other Restrictions on Lies 172 References 175 Chapter 9 Optimal Search in One Variable 177 9.1 Midpoint Strategy 177 9.2 Fibonacci Search 179 9.3 Minimum Root Identification 183 References 190 Chapter 10 Unbounded Search 193 10.1 Introduction 193 10.2 Bentley-Yao Algorithms 195 10.3 Search with Lies 199 10.4 Unbounded Fibonacci Search 200 References 202 Chapter 11 Group Testing on Graphs 203 11.1 On Bipartite Graphs 203 11.2 On Graphs 205 11.3 On Hypergraphs 207 11.4 On Trees 212 11.5 Other Constraints 216 References 217 Chapter 12 Membership Problems 218 12.1 Examples 218 12.2 Polyhedral Membership 220 12.3 Boolean Formulas and Decision Trees 222 12.4 Recognition of Graph Properties 226 References 229 Chapter 13 Complexity Issues 231 13.1 General Notions 231 13.2 The Prototype Problem is in PSPACE 233 x Contents 13.3 Consistency 234 13.4 Determinacy 236 13.5 On Sample Space S(n) 237 13.6 Learning by Examples 243 References 244 Index 245