Explicitly invokes the garbage collector.
This predicate invokes the garbage collector to reclaim data structures in the heap that are no longer accessible to the computation.
No expansion of the heap is done, even if
gc_margin kilobytes cannot
be reclaimed (see ref-lps-flg-cha). This means that calls to this
predicate are effective only when the heap contains a significant
amount of garbage.
The cut may be used in conjunction with
garbage_collect/0 to allow code
that works in cycles and builds up large data structures to run for more
cycles without running out of memory. The cut removes any alternatives that
may be pending, thus potentially freeing up garbage that could not otherwise
In the code fragment:
cycle(X) :- big_goal(X, X1), cycle(X1).
cycle/1 is to run for a long time, and if
generates a lot of garbage, then rewrite the code like this:
cycle(X) :- big_goal(X, X1), !, garbage_collect, cycle(X1).
Use of the
!, garbage_collect idiom is only
desirable when you notice that your code does frequent garbage
collections. It will allow the garbage collector to collect garbage
more effectively, and the cycle will run without demanding increasing
amounts of memory.