Parallel Nondeterministic Programming as a Language Extension to C (Short Paper)

This paper explores parallel nondeterministic programming as an extension to the C programming language; it provides constructs for specifying code containing ambiguous choice as introduced by McCarthy. A translator to plain C code was implemented as an extension to the ableC language specification. Translation involves a transformation to continuation passing style, providing lazy choice by storing continuation closures in a separate task buffer. This exploration considers various search evaluation approaches and their impact on correctness and performance. Multiple search drivers were implemented, including single-Threaded depth-first search, a combined breadth-And depth-first approach, as well as two approaches to parallelism. Several benchmark applications were created using the extension, including n-Queens, SAT, and triangle peg solitaire. The simplest parallel search driver, using independent threads, showed the best performance in most cases, providing a significant speedup over the sequential versions. Adding task sharing between threads showed similar or slightly improved performance.