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garbage_collect

Request an immediate garbage collection.

Description

Causes an immediate garbage collection of the global and trail stack, provided that the garbage collector is not switched off (cf. set_flag/2). In any case the predicate succeeds.

Note that the garbage collector is usually triggered automatically, controlled by the user-definable flag gc_interval. Therefore, the usage of garbage_collect/0 should be restricted to situations where the automatic triggering performs badly. In this case it should be inserted in a place where it is known for sure that a lot of structures and lists have become useless, eg. just before a tail-recursive call as shown in the example.

Modes and Determinism

Examples

cycle(OldState) :-
    transform(OldState, NewState), /* long computation     */
    !,
    garbage_collect,               /* OldState is obsolete */
    cycle(NewState).

See Also

env / 0, set_flag / 2, get_flag / 2