experimental extension for evaluating forms in parallel
Major Section:  ACL2 Documentation

This documentation topic relates to an experimental extension of ACL2, created initially by David L. Rager. See parallelism-build for how to build an executable image that supports parallel evaluation. Also see books/parallel for examples.

One of ACL2's strengths lies in its ability to execute industrial models efficiently. The ACL2 source code provides an experimental parallel evaluation capability that can increase the speed of explicit evaluation, including simulator runs using such models, and it can also decrease the time required for proofs that make heavy use of the evaluation of ground terms.

The parallelism primitives are plet, pargs, pand, and por. Pand and por terminate early when an argument is found to evaluate to nil or non-nil, respectively, thus potentially improving on the efficiency of lazy evaluation.

Some Related Topics

The parallelism primitives allow for limiting parallel evaluation (spawning of so-called ``threads'') depending on resource availability. Specifically, the primitives allow specification of a size condition to control the granularity under which threads are allowed to spawn. You can use such granularity declarations in recursively-defined functions to implement data-dependent parallelism in their execution.

We recommend that in order to learn to use the parallelism primitives, you begin by reading examples: see parallelism-tutorial. That section will direct you to further documentation topics.