Goal is executed as if called via call(Goal), but only for a maximum of TimeLimit seconds. If the goal is still executing after TimeLimit, time-out occurs, the execution of the goal is terminated (via throw/1) and TimeOutGoal is executed. If the value of TimeLimit is 0 or 1.0Inf, no timeout is applied to the Goal.
Note that, if Goal is nondeterministic, execution flow may leave the scope of timeout/3 on success and re-enter on failure. In this case, only time spent within Goal will be counted towards the TimeLimit.
The predicate is based on the after event timers, so TimeLimit is measured in the timer currently used by after events. The current time used for the associated event timer can be retrieved using statistics(event_time, CurrentTime). The timeout predicate can be used with other after events, and can be nested within itself (i.e. embedded within Goal or TimeOutGoal).
Note that timeout/3 can be defined in terms of timeout/7 as:
timeout(Goal, TimeLimit, TimeOutGoal) :-
timeout(Goal, TimeLimit, TimeOutGoal, all_solution, _, _, _).
?- timeout((repeat,fail), 1.5, writeln(timed-out)). % time-out from infinite loop
timed - out
Yes (1.51s cpu)