[ Predicate Database and Compiler | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]

parallel +SpecList

Declares the procedure(s) specified by SpecList as parallel.
+SpecList
Comma-separated sequence of expressions of the form Atom/Integer.

Description

The parallel annotation specifies that the system is allowed to execute the clauses of the annotated predicate in parallel (Or-parallelism), instead of sequentially by backtracking. This has the following consequences:

* the predicate is a source of or-parallelism which will hopefully speed up execution of the program on a parallel machine

* calls to this predicate may return alternative solutions in unpredictable order

* side effects within the parallel execution may happen in unpredictable order

The parallel annotation has simply no effect when the predicate (or a particular call to it) is deterministic or when it is used with a sequential ECLiPSe system.

A procedure can be declared parallel before it is actually defined.

Fail Conditions

None.

Resatisfiable

No.

Exceptions

(4) instantiation fault
SpecList is not instantiated.
(5) type error
SpecList is instantiated, but not to a sequence of expressions of the form Atom/Integer.

Examples

  [eclipse 1]: [user].
   :- parallel p/1.
   p(a).  p(b).  p(c).
  user       compiled traceable 220 bytes in 0.02 seconds
  yes.
  [eclipse 2]: get_flag(p/1, parallel, Flag).
  Flag = on
  yes.
  [eclipse 3]: p(X), use(X).
  % The three clauses of p/1 as well as the resulting goals
  % use(a), use(b) and use(c) may be executed in parallel!

See Also

compile / 1, get_flag / 3, set_flag / 3