Lazy Task Creation Research Articles

An Enhancement of Futures Runtime in Presence of Cache Memory Hierarchy

A future is a simple abstraction mechanism for exposing potential concurrency in programs. In this paper, we propose an enhancement of our previously developed runtime for scheduling and executing futures based on the lazy task creation technique that aims to reflect the cache memory hierarchy present in modern multi-core and multiprocessor systems.

Supporting dynamic data structures on distributed-memory machines

Compiling for distributed-memory machines has been a very active research area in recent years. Much of this work has concentrated on programs that use arrays as their primary data structures. To date, little work has been done to address the problem of supporting programs that use pointer-based dynamic data structures. The techniques developed for supporting SPMD execution of array-based programs rely on the fact that arrays are statically defined and directly addressable. Recursive data structures do not have these properties, so new techniques must be developed. In this article, we describe an execution model for supporting programs that use pointer-based dynamic data structures. This model uses a simple mechanism for migrating a thread of control based on the layout of heap-allocated data and introduces parallelism using a technique based on futures and lazy task creation. We intend to exploit this execution model using compiler analyses and automatic parallelization techniques. We have implemented a prototype system, which we callOlden, that runs on the Intel iPSC/860 and the Thinking Machines CM-5. We discuss our implementation and report on experiments with five benchmarks.

Continuation-based compilation of functional languages for parallel machines

We tackle the problems of correctness and efficiency of paralled implementations of functional languages. We present a compilation technique described in terms of program transformations in the functional framework. The original functional expression is transformed into a functional term, which can be seen as traditional machine code. The main feature of the parallel implementation is the use of continuations. We introduce a parallel abstract machine describing lazy task creation in terms of exportation of continuations. The advantages of the approach are twofold: (1)correetness proofs are made simpler and (2) the implementation is efficient because the use of continuations reduces the task management overhead.

Lazy task creation: a technique for increasing the granularity of parallel programs

When a parallel algorithm is written naturally, the resulting program often produces tasks of a finer grain than an implementation can exploit efficiently. Two solutions to the granularity problem that combine parallel tasks dynamically at runtime are discussed. The simpler load-based inlining method, in which tasks are combined based on dynamic bad level, is rejected in favor of the safer and more robust lazy task creation method, in which tasks are created only retroactively as processing results become available. The strategies grew out of work on Mul-T, an efficient parallel implementation of Scheme, but could be used with other languages as well. Mul-T implementations of lazy task creation are described for two contrasting machines, and performance statistics that show the method's effectiveness are presented. Lazy task creation is shown to allow efficient execution of naturally expressed algorithms of a substantially finer grain than possible with previous parallel Lisp systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>