"No Such Thing as Luck: Improving Parallel Programmability with Determinism"

Abstract:

Nondeterminism is a key complication in programming multicore systems. It makes testing more difficult and less useful, since another run of the program can potentially introduce new behaviors. Nondeterminism also frustrates debugging efforts by making bugs hard to reproduce. Previous approaches to coping with nondeterminism in parallel programs have focused on recording an execution for subsequent replay, or required that programs be written in restrictive languages, but have not addressed the underlying nondeterminism of multicore systems in a direct way.

In this talk, I will show how to use novel hardware and software techniques to provide deterministic execution for arbitrary parallel programs written in today's languages. I've built a series of deterministic platforms, from new hardware architectures to compilers and language extensions, that show how the challenge of nondeterminism can be addressed across the computing stack. Hardware speculation, memory consistency relaxations, and hardware-software co-design all play key roles in improving the performance and simplicity of determinism. I'll also share my plans for future work, from leveraging determinism to accelerate safety and security checks, to new parallel computer architectures that enable a unified task+data parallelism abstraction.

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