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/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2010-2019, University of Amsterdam
CWI, Amsterdam
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
:- module(timeout,
[ time_out/3 % :Goal, +Time, -Result
]).
:- use_module(library(time)).
/** <module> SICStus 3-compatible library(timeout).
@author Ulrich Neumerkel
@author Jan Wielemaker
@see https://sicstus.sics.se/sicstus/docs/3.12.11/html/sicstus/Timeout.html
*/
:- meta_predicate
time_out(0, +, -).
%! time_out(:Goal, +Time_ms, -Result) is nondet.
%
% This library provides a SICStus compatible implementation of
% time-outs. This predicate runs Goal as call/1 and binds Result to
% either `success` (the answer was produced within Time_ms) or
% `time_out` (Goal did not terminate within Time_ms). If Goal
% succeeds with a choice point, backtracking into it re-applies the
% time limit, i.e., each solution gets a Time_ms time limit.
%
% Calls to time_out/3 can be nested. If an outer time out is
% triggered first, the inner time out is cancelled using a
% time_out(Id) exception and the outer one binds Result to
% `time_out`.
%
% @bug Unfortunately, our emulation is not fully compatible with the
% SICStus original. Notably, Time is measured in __wall-time instead
% of virtual CPU time__. Virtual CPU time is hard in
% threaded-environments. On most systems, you probably need a thread
% that measures the CPU usage of the monitored thread.
%
% @see alarm/3, call_with_time_limit/2, call_with_inference_limit/3
% and thread-based primitives such as thread_signal/2 and
% first_solution/3.
time_out(Goal, Time_ms, Result) :-
Time_s is (Time_ms//1)/1000,
prolog_current_frame(Fid), % Unique id for this call.
catch( ( Result0 = success,
setup_call_cleanup(
alarm(Time_s, throw(time_out(Fid)), Id),
Goal,
( Removed = true, remove_alarm(Id) )),
( var(Removed)
-> uninstall_alarm(Id),
( true ; install_alarm(Id,Time_s), fail )
; true
)
),
time_out(Fid),
Result0 = time_out ),
Result = Result0.
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