Transparent concurrent execution of mutually exclusive alternatives

The task of concurrently computing alternative solutions to a problem where only one of the solutions is needed is examined. In this case the rule for selecting between the solutions is faster first, where the first successful alternative is selected. For problems where the required execution time is unpredictable, this method shows substantial execution time performance increases over other methods. In order to test the utility of the design, it is used for two application areas: distributed execution of recovery blocks and OR-parallelism in Prolog. The authors present: (1) a model for selection of alternatives in a sequential setting: (2) a transformation that allows alternatives to execute concurrently; (3) a description of the semantics-preservation mechanism; and (4) parameterization of where the performance improvements can be expected. Additionally, examples of application areas for the method are given