Scheduling and synchronization for multicore concurrency platforms

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 217-230).Developing correct and efficient parallel programs is difficult since programmers often have to manage low-level details like scheduling and synchronization explicitly. Recently, however, many hardware vendors have been shifting towards building multicore computers. This trend creates an enormous pressure to create concurrency platforms - platforms that provide an easier interface for parallel programming and enable ordinary programmers to write scalable, portable and efficient parallel programs. This thesis provides some provably-good practical solutions to problems that arise in the implementation of concurrency platforms, particularly in the domain of scheduling and synchronization. The first part of this thesis describes work on scheduling of parallel programs written in dynamic multithreaded languages (such as Cilk, Hood etc.). These languages allow the programmer to express parallelism of their code in a natural manner, while an automatic scheduler in the concurrency platform is responsible for scheduling the program on the underlying parallel hardware. This thesis presents designs to increase the functionality of these concurrency platforms. The second part of the thesis presents work on transactional memory semantics and design. Transactional memory (TM), has been recently proposed as an alternative to locks. TM provides a transactional interface to memory. The programmers can specify their critical sections inside a transaction, and the TM concurrency platform guarantees that the region executes atomically. One of the purported advantages of TM over locks is that transactional code is composable.(cont.) Most of the current TM concurrency platforms do not support full composability, however. This thesis addresses two of the composability problems in existing TM concurrency platforms.by Kunal Agrawal.Ph.D

Composable abstractions for synchronization in dynamic threading platforms

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 259-269).High-level abstractions for parallel programming simplify the development of efficient parallel applications. In particular, composable abstractions allow programmers to construct a complex parallel application out of multiple components, where each component itself may be designed to exploit parallelism. This dissertation presents the design of three composable abstractions for synchronization in dynamic-threading platforms, based on ideas of task-graph execution, helper locks, and transactional memory. These designs demonstrate provably efficient runtime scheduling for programs with synchronization. For applications that use task-graph synchronization, I demonstrate provably efficient execution of task graphs with arbitrary dependencies as a library in a fork-join platform. Conventional wisdom suggests that a fork-join platform can execute an arbitrary task graph only with special runtime support or by converting the graph into a series-parallel computation which has less parallelism. By implementing Nabbit, a Cilk++ library for arbitrary task-graph execution, I show that one can in fact avoid introducing runtime modifications or additional constraints on parallelism. Nabbit achieves an asymptotically optimal completion-time bound for task graphs with constant degree. For applications that use lock-based synchronization, I introduce helper locks, a new synchronization abstraction that enables programmers to exploit asynchronous task parallelism inside locked critical regions. When a processor fails to acquire a helper lock, it can help complete the parallel critical region protected by the lock instead of simply waiting for the lock to be released. I also present HELPER, a runtime for supporting helper locks, and prove theoretical performance bounds which imply that HELPER achieves linear speedup on programs with a small number of highly parallel critical regions. For applications that use transaction-based synchronization, I present CWSTM, the first design of a transactional memory (TM) system that supports transactions with nested parallelism and nested parallel transactions of unbounded nesting depth. CWSTM demonstrates that one can provide theoretical bounds on the overhead of transaction conflict detection which are independent of nesting depth. I also introduce the concept of ownership-aware TM, the idea of using information about which memory locations a software module owns to provide provable guarantees of safety and correctness for open-nested transactions.by Jim Sukha.Ph.D

The 1991 3rd NASA Symposium on VLSI Design

Papers from the symposium are presented from the following sessions: (1) featured presentations 1; (2) very large scale integration (VLSI) circuit design; (3) VLSI architecture 1; (4) featured presentations 2; (5) neural networks; (6) VLSI architectures 2; (7) featured presentations 3; (8) verification 1; (9) analog design; (10) verification 2; (11) design innovations 1; (12) asynchronous design; and (13) design innovations 2

First International Conference on Ada (R) Programming Language Applications for the NASA Space Station, volume 2

Topics discussed include: reusability; mission critical issues; run time; expert systems; language issues; life cycle issues; software tools; and computers for Ada