Teaching Parallelism with River Trail

Parallel hardware is today’s reality and parallel programming mod-els exist for most mainstream languages. Surprisingly JavaScript, the mother tongue of the web, is still stuck in its sequential past. JavaScript’s unique programming model, the web’s safety and se-curity requirements, and the expectations of its programmers for determinism have impeded parallelization until now. Parallel JavaScript (code named River Trail) is a set of JavaScript extensions and an API that provides safe, deterministic parallelism to web applications while fitting within the event-driven, secu-rity oriented world of JavaScript applications. River Trail allows programmers to utilize available hardware parallelism on client machines- from SIMD units to multiple cores, using high-level parallel programming patterns. In this paper we describe River Trail, show how it can be used to provide a gentle introduction to parallelism using our self-contained hands-on tutorial. At the end of the tutorial the student will have mastered the basic concepts of parallel programming and use this knowledge to build a realistic parallel HTML5 web application in River Trail. 1