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Defthms about zip and tie: Reasoning about powerlists in ACL2
 Univ. of Texas Comp. Sci. Tech. Rep
, 1997
"... In [Mis94], Misra introduced the powerlist data structure, which is well suited to express recursive, dataparallel algorithms. Moreover, Misra and other researchers have shown how powerlists can be used to prove the correctness of several algorithms. This success has encouraged some researchers to ..."
Abstract

Cited by 8 (3 self)
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In [Mis94], Misra introduced the powerlist data structure, which is well suited to express recursive, dataparallel algorithms. Moreover, Misra and other researchers have shown how powerlists can be used to prove the correctness of several algorithms. This success has encouraged some researchers to pursue automated proofs of theorems about powerlists[Kap97, KS95a, KS95b]. In this paper, we show how ACL2 can be used to verify theorems about powerlists. We depart from previous approaches in two significant ways. First, the powerlists we use are not the regular structures defined by Misra; that is, we do not require powerlists to be balanced trees. As we will see, this complicates some of the proofs, but on the other hand it allows us to state theorems that are otherwise beyond the language of powerlists. Second, we wish to prove the correctness of powerlist algorithms as much as possible within the logic of powerlists. Previous approaches have relied
Data Structures for Parallel Recursion
, 1997
"... vii Chapter 1 Introduction 1 1.1 Synchronous Parallel Programming . . . . . . . . . . . . . . . . . . . 4 1.2 Basic Definitions and Notations . . . . . . . . . . . . . . . . . . . . . 6 1.2.1 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2.2 Operator Priority . . . . . . . ..."
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Cited by 2 (0 self)
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vii Chapter 1 Introduction 1 1.1 Synchronous Parallel Programming . . . . . . . . . . . . . . . . . . . 4 1.2 Basic Definitions and Notations . . . . . . . . . . . . . . . . . . . . . 6 1.2.1 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2.2 Operator Priority . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.2.3 Notation and Proof Style . . . . . . . . . . . . . . . . . . . . 9 1.3 Cost Calculus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.3.1 Parallel Algorithm Complexity . . . . . . . . . . . . . . . . . 14 1.3.2 Parallel Computation Models . . . . . . . . . . . . . . . . . . 17 Chapter 2 Powerlists 20 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.1.1 Induction Principle for PowerLists . . . . . . . . . . . . . . . . 25 2.1.2 Data Movement and Permutation Functions . . . . . . . . . . 26 2.2 Hypercubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.3 A Cost Calculus for P...
A Formalization of Powerlist Algebra in ACL2
"... Abstract. In [16], Misra introduced the powerlist data structure, which is well suited to express recursive, dataparallel algorithms. Moreover, Misra and other researchers have shown how powerlists can be used to prove the correctness of several algorithms. This success has encouraged some research ..."
Abstract
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Abstract. In [16], Misra introduced the powerlist data structure, which is well suited to express recursive, dataparallel algorithms. Moreover, Misra and other researchers have shown how powerlists can be used to prove the correctness of several algorithms. This success has encouraged some researchers to pursue automated proofs of theorems about powerlists [7, 8, 9]. In this paper, we show how ACL2 can be used to verify theorems about powerlists. We depart from previous approaches in two significant ways. First, the powerlists we use are not the regular structures defined by Misra; that is, we do not require powerlists to be balanced trees. As we will see, this complicates some of the proofs, but on the other hand it allows us to state theorems that are otherwise beyond the language of powerlists. Second, we wish to prove the correctness of powerlist algorithms as much as possible within the logic of powerlists. Previous approaches have relied on intermediate lemmas which are unproven (indeed unstated) within the powerlist logic. However, we believe these lemmas must be formalized if the final theorems are to be used as a foundation for subsequent work, e.g., in the verification of system libraries. In our experience, some of these unproven lemmas presented the biggest obstacle to finding an automated proof. We illustrate our approach with two case studies involving Batcher sorting and prefix sums.