Independent and-parallel execution

Author(s): Manuel Hermenegildo, Manuel Carro.

Version: 1.5#118 (2000/4/19, 18:13:43 CEST)

Version of last change: 1.3#120 (1999/11/26, 12:5:17 MET)

This library allows and-parallel execution of goals in (Herbrand-)independent fashion. It resembles the execution rules of &-Prolog [HG90]. Basically, goals are run in and-parallel provided that their arguments do not share bindings, i.e., are not bound to terms which contain a common variable.

Beware: it is highly unstable at the moment!

• Usage and interface (andprolog)
• Documentation on exports (andprolog)
• Known bugs and planned improvements (andprolog)

Usage and interface (andprolog)

Documentation on exports (andprolog)

PREDICATE: @&/2:

@&(GoalA,GoalB)

GoalA and GoalB are run in independent and-parallel fashion. This is just a first sketch, and valid only for deterministic independent goals.

Meta-predicate with arguments: @&(goal,goal).

PREDICATE: =>/2:

=>(A,B)

If A is true B is run in parallel, otherwise sequentially.

Meta-predicate with arguments: =>(goal,goal).

Usage: =>(A,B)

• The following properties should hold at call time: B is of the form goal&goal. (andprolog:andcallable/1)
• The following properties hold globally: Documentation is still incomplete: =>(A,B) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PROPERTY: indep/1:

indep(X)

The variables in each pair of the list X are pairwise independent.

Usage: indep(X)

• Description: The variables in pairs in X are pairwise independent.

PROPERTY: indep/2:

indep(X,Y)

X and Y are independent, i.e., they are bound to terms which have no variables in common. For example, indep(X,Y) holds for X=f(Z),Y=g(K) and also for X=f(a),Y=X (since both X and Y are bound to ground terms). It does not hold for X=f(Z),Y=g(Z) and for X=Y.

Usage: indep(X,Y)

• Description: X and Y do not have variables in common.

PREDICATE: active_agents/1:

Usage: active_agents(?(NumberOfAgents))

• Description: Tests/sets the number of active agents looking for goals to execute. As for now, those agents are resource-consuming, even when they are just looking for work, and not executing any user goals.
• The following properties should hold at call time: ?(NumberOfAgents) is an integer. (basic_props:int/1)

Known bugs and planned improvements (andprolog)

• The fact that only the first solution is returned for the conjunction is due to performance matters, and we expect to remove it in a near future.
• CGEs (i.e., =>) are not supported.
• The indep/1, indep/2, and ground/1 are not very efficient; they might be replaced by native versions in a future.

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