Process-Oriented Parallel Programming with an Application to Data-Intensive Computing

We introduce process-oriented programming as a natural extension of object-oriented programming for parallel computing. It is based on the observation that every class of an object-oriented language can be instantiated as a process, accessible via a remote pointer. The introduction of process pointers requires no syntax extension, identifies processes with programming objects, and enables processes to exchange information simply by executing remote methods. Process-oriented programming is a high-level language alternative to multithreading, MPI and many other languages, environments and tools currently used for parallel computations. It implements natural object-based parallelism using only minimal syntax extension of existing languages, such as C++ and Python, and has therefore the potential to lead to widespread adoption of parallel programming. We implemented a prototype system for running processes using C++ with MPI and used it to compute a large three-dimensional Fourier transform on a computer cluster built of commodity hardware components. Three-dimensional Fourier transform is a prototype of a data-intensive application with a complex data-access pattern. The process-oriented code is only a few hundred lines long, and attains very high data throughput by achieving massive parallelism and maximizing hardware utilization.Comment: 20 pages, 1 figur

Natural language and programming: designing effective environments for novices

Given the current drive to teach computational concepts to all from an early age, we consider whether traditional programming languages are truly necessary, or whether natural language might be a suitable medium for program generation and comprehension, given its familiarity and ubiquity. We conducted an empirical study on the use of natural language for computation, and found that, although it provides support for understanding computational concepts, it introduces additional difficulties when used for coding. Following a design study with target users, we distilled our findings into a series of design guidelines for novice programming environments that incorporate natural language. These guidelines drove the design of Flip, a bimodal programming language for young people's game creation activities. Two empirical studies examined the extent to which these embodied design guidelines support ease of use and an understanding of computation. The guidelines have potential both for analysing the usability of existing novice programming environments, and for designing new ones

Dependent Merges and First-Class Environments

In most programming languages a (runtime) environment stores all the definitions that are available to programmers. Typically, environments are a meta-level notion, used only conceptually or internally in the implementation of programming languages. Only a few programming languages allow environments to be first-class values, which can be manipulated directly in programs. Although there is some research on calculi with first-class environments for statically typed programming languages, these calculi typically have significant restrictions. In this paper we propose a statically typed calculus, called ?_i, with first-class environments. The main novelty of the ?_i calculus is its support for first-class environments, together with an expressive set of operators that manipulate them. Such operators include: reification of the current environment, environment concatenation, environment restriction, and reflection mechanisms for running computations under a given environment. In ?_i any type can act as a context (i.e. an environment type) and contexts are simply types. Furthermore, because ?_i supports subtyping, there is a natural notion of context subtyping. There are two important ideas in ?_i that generalize and are inspired by existing notions in the literature. The ?_i calculus borrows disjoint intersection types and a merge operator, used in ?_i to model contexts and environments, from the ?_i calculus. However, unlike the merges in ?_i, the merges in ?_i can depend on previous components of a merge. From implicit calculi, the ?_i calculus borrows the notion of a query, which allows type-based lookups on environments. In particular, queries are key to the ability of ?_i to reify the current environment, or some parts of it. We prove the determinism and type soundness of ?_i, and show that ?_i can encode all well-typed ?_i programs

Learning to communicate computationally with Flip: a bi-modal programming language for game creation

Teaching basic computational concepts and skills to school children is currently a curricular focus in many countries. Running parallel to this trend are advances in programming environments and teaching methods which aim to make computer science more accessible, and more motivating. In this paper, we describe the design and evaluation of Flip, a programming language that aims to help 11–15 year olds develop computational skills through creating their own 3D role-playing games. Flip has two main components: 1) a visual language (based on an interlocking blocks design common to many current visual languages), and 2) a dynamically updating natural language version of the script under creation. This programming-language/natural-language pairing is a unique feature of Flip, designed to allow learners to draw upon their familiarity with natural language to “decode the code”. Flip aims to support young people in developing an understanding of computational concepts as well as the skills to use and communicate these concepts effectively. This paper investigates the extent to which Flip can be used by young people to create working scripts, and examines improvements in their expression of computational rules and concepts after using the tool. We provide an overview of the design and implementation of Flip before describing an evaluation study carried out with 12–13 year olds in a naturalistic setting. Over the course of 8 weeks, the majority of students were able to use Flip to write small programs to bring about interactive behaviours in the games they created. Furthermore, there was a significant improvement in their computational communication after using Flip (as measured by a pre/post-test). An additional finding was that girls wrote more, and more complex, scripts than did boys, and there was a trend for girls to show greater learning gains relative to the boys

Keyboardless Visual Programming Using Voice, Handwriting, and Gesture

Visual programming languages have facilitated the application development process, improving our ability to express programs, as well as our ability to view, edit and interact with them. Yet even in programming environments, productivity is restricted by the primary input sources: the mouse and the keyboard. As an alternative, we investigate a program development interface which responds to the most natural human communication technologies: voice, handwriting and gesture. Speech- and pen-based systems have yet to find broad acceptance in everyday life because they are insufficiently advantageous to overcome problems with reliability. However, we believe that a visual programming environment with a multimodal user interface properly constrained so as not to exceed the limits of the current technology has the potential to increase programming productivity for not only those people who are manually or visually impaired, but for the general population as well. In this paper we report on such a system