Scheduling Transformation and Dependence Tests for Recursive Programs

Scheduling transformations reorder the execution of operations in a program to improve locality and/or parallelism. The polyhedral model provides a general framework for performing instance-wise scheduling transformations for regular programs, reordering the iterations of loops that operate over dense arrays through transformations like tiling. There is no analogous framework for recursive programs—despite recent interest in optimizations like tiling and fusion for recursive applications. This paper presents PolyRec, the first general framework for applying scheduling transformations—like inlining, interchange, and code motion—to nested recursive programs and reasoning about their correctness. We describe the phases of PolyRec—representing dynamic instances, applying transformations, reasoning about correctness—and show that PolyRec is able to apply sophisticated, composed transformations to complex, nested recursive programs and improve performance through enhanced locality

Parametric Heap Abstraction for Dynamic Language Libraries

For commercial development, dynamic languages are growing in popularity. Consequently, dynamic language developers must consider the correctness of their code. Deployment of correct or sufficiently correct code is critical to the success and adoption of that code. However, it is challenging to ensure the correctness of dynamic language code when it is a library. Inputs to dynamic language libraries are often not simple values. They can also be open objects, which permit adding, removing, and iterating over attribute names, and they can be functions that may be called. Furthermore, the result of running library functions on objects is often new objects derived from the input objects. To ensure the correctness of dynamic language libraries, this dissertation uses static analysis. Static analysis is typically used to infer facts about programs' values, but in these dynamic language libraries, values can be objects and functions. These objects may be unknown and thus have an unknown set of attribute names because they are inputs or these objects may be iteratively derived from other objects. Functions may be stored, called, or wrapped in other functions, regardless of if they are known or not. A static analysis for dynamic language libraries must handle these cases. To support static analysis of libraries, this dissertation introduces local heap abstractions suitable for representing parts of memory that library code may affect. These abstractions build upon abstractions for sets that enable representing relations between attribute names of otherwise unknown objects. Furthermore, the local reasoning is utilized to abstract the effect of calling unknown functions. The precision of these abstractions are demonstrated on a range of small, but complex JavaScript-inspired examples. The examples are extracted from libraries such as Traits.js and Google Closure

SWI-Prolog and the Web

Where Prolog is commonly seen as a component in a Web application that is either embedded or communicates using a proprietary protocol, we propose an architecture where Prolog communicates to other components in a Web application using the standard HTTP protocol. By avoiding embedding in external Web servers development and deployment become much easier. To support this architecture, in addition to the transfer protocol, we must also support parsing, representing and generating the key Web document types such as HTML, XML and RDF. This paper motivates the design decisions in the libraries and extensions to Prolog for handling Web documents and protocols. The design has been guided by the requirement to handle large documents efficiently. The described libraries support a wide range of Web applications ranging from HTML and XML documents to Semantic Web RDF processing. To appear in Theory and Practice of Logic Programming (TPLP)Comment: 31 pages, 24 figures and 2 tables. To appear in Theory and Practice of Logic Programming (TPLP

Preservice Teachers’ Algebraic Reasoning and Symbol Use on a Multistep Fraction Word Problem

Previous research on preservice teachers’ understanding of fractions and algebra has focused on one or the other. To extend this research, we examined 85 undergraduate elementary education majors and middle school mathematics education majors’ solutions and solution paths (i.e., the ways or methods in which preservice teachers solve word problems) when combining fractions with algebra on a multistep word problem. In this article, we identify and describe common strategy clusters and approaches present in the preservice teachers’ written work. Our results indicate that preservice teachers’ understanding of algebra include arithmetic methods, proportions, and is related to their understanding of a whole

Web Services: A Process Algebra Approach

It is now well-admitted that formal methods are helpful for many issues raised in the Web service area. In this paper we present a framework for the design and verification of WSs using process algebras and their tools. We define a two-way mapping between abstract specifications written using these calculi and executable Web services written in BPEL4WS. Several choices are available: design and correct errors in BPEL4WS, using process algebra verification tools, or design and correct in process algebra and automatically obtaining the corresponding BPEL4WS code. The approaches can be combined. Process algebra are not useful only for temporal logic verification: we remark the use of simulation/bisimulation both for verification and for the hierarchical refinement design method. It is worth noting that our approach allows the use of any process algebra depending on the needs of the user at different levels (expressiveness, existence of reasoning tools, user expertise)