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yap-6.3/library/c_alarms.yap
Theofrastos Mantadelis b57859f28b fixed some typos
2011-02-04 16:08:18 +01:00

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Prolog

%%% -*- Mode: Prolog; -*-
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Concurrent alarms was developed at Katholieke Universiteit Leuven
%
% Copyright 2010
% Katholieke Universiteit Leuven
%
% Contributions to this file:
% Author: Theofrastos Mantadelis
% $Date: 2011-02-04 16:04:49 +0100 (Fri, 04 Feb 2011) $
% $Revision: 11 $
% Contributions: The timer implementation is inspired by Bernd Gutmann's timers
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
:- module(c_alarms, [set_alarm/3,
unset_alarm/1,
time_out_call_once/3,
timer_start/1,
timer_restart/1,
timer_stop/2,
timer_elapsed/2,
timer_pause/2]).
% set_alarm(+Seconds, +Execute, -ID)
% calls Executes after a time interval of Seconds
% ID is returned to be able to unset the alarm (the call will not be executed)
% set_alarm/3 supports multiple & nested settings of alarms.
% Known Bug: There is the case that an alarm might trigger +-1 second of the set time.
%
% unset_alarm(+ID)
% It will unschedule the alarm.
% It will not affect other concurrent alarms.
%
% time_out_call(+Seconds, +Goal, -Return)
% It will will execute the closure Goal and returns its success or failure at Return.
% If the goal times out in Seconds then Return = timeout.
:- use_module(library(lists), [member/2, memberchk/2, delete/3]).
:- use_module(library(ordsets), [ord_add_element/3]).
:- use_module(library(apply_macros), [maplist/3]).
:- dynamic('$timer'/3).
:- meta_predicate(set_alarm(+, 0, -)).
:- meta_predicate(time_out_call_once(+, 0, -)).
:- meta_predicate(prove_once(0)).
:- initialization(local_init).
local_init:-
bb_put(alarms, []),
bb_put(identity, 0).
get_next_identity(ID):-
bb_get(identity, ID),
NID is ID + 1,
bb_put(identity, NID).
set_alarm(Seconds, Execute, ID):-
bb_get(alarms, []),
get_next_identity(ID), !,
bb_put(alarms, [alarm(Seconds, ID, Execute)]),
alarm(Seconds, alarm_handler, _).
set_alarm(Seconds, Execute, ID):-
get_next_identity(ID), !,
bb_get(alarms, [alarm(CurrentSeconds, CurrentID, CurrentExecute)|Alarms]),
alarm(0, true, Remaining),
Elapsed is CurrentSeconds - Remaining - 1,
maplist(subtract(Elapsed), [alarm(CurrentSeconds, CurrentID, CurrentExecute)|Alarms], RemainingAlarms),
ord_add_element(RemainingAlarms, alarm(Seconds, ID, Execute), [alarm(NewSeconds, NewID, NewToExecute)|NewAlarms]),
bb_put(alarms, [alarm(NewSeconds, NewID, NewToExecute)|NewAlarms]),
alarm(NewSeconds, alarm_handler, _).
set_alarm(Seconds, Execute, ID):-
throw(error(permission_error(create, alarm, set_alarm(Seconds, Execute, ID)), 'Non permitted alarm identifier.')).
subtract(Elapsed, alarm(Seconds, ID, Execute), alarm(NewSeconds, ID, Execute)):-
NewSeconds is Seconds - Elapsed.
unset_alarm(ID):-
\+ ground(ID),
throw(error(instantiation_error, 'Alarm ID needs to be instantiated.')).
unset_alarm(ID):-
bb_get(alarms, Alarms),
\+ memberchk(alarm(_Seconds, ID, _Execute), Alarms),
throw(error(existence_error(alarm, unset_alarm(ID)), 'Alarm does not exist.')).
unset_alarm(ID):-
alarm(0, true, Remaining),
bb_get(alarms, Alarms),
[alarm(Seconds, _, _)|_] = Alarms,
Elapsed is Seconds - Remaining - 1,
delete_alarm(Alarms, ID, NewAlarms),
bb_put(alarms, NewAlarms),
(NewAlarms = [alarm(NewSeconds, _, _)|_] ->
RemainingSeconds is NewSeconds - Elapsed,
alarm(RemainingSeconds, alarm_handler, _)
;
true
).
delete_alarm(Alarms, ID, NewAlarms):-
memberchk(alarm(Seconds, ID, Execute), Alarms),
delete(Alarms, alarm(Seconds, ID, Execute), NewAlarms).
alarm_handler:-
bb_get(alarms, [alarm(_, _, CurrentExecute)|[]]),
bb_put(alarms, []),
call(CurrentExecute).
alarm_handler:-
bb_get(alarms, [alarm(Elapsed, CurrentID, CurrentExecute)|Alarms]),
maplist(subtract(Elapsed), Alarms, NewAlarms),
find_zeros(NewAlarms, ZeroAlarms),
findall(alarm(S, ID, E), (member(alarm(S, ID, E), NewAlarms), S > 0), NonZeroAlarms),
bb_put(alarms, NonZeroAlarms),
(NonZeroAlarms = [alarm(NewSeconds, _, _)|_] ->
alarm(NewSeconds, alarm_handler, _)
;
true
),
execute([alarm(0, CurrentID, CurrentExecute)|ZeroAlarms]).
find_zeros([], []).
find_zeros([alarm(0, ID, E)|T], [alarm(0, ID, E)|R]):-
find_zeros(T, R).
find_zeros([alarm(S, _, _)|T], R):-
S > 0,
find_zeros(T, R).
execute([]).
execute([alarm(_, _, Execute)|R]):-
call(Execute),
execute(R).
time_out_call_once(Seconds, Goal, Return):-
bb_get(identity, ID),
set_alarm(Seconds, throw(timeout(ID)), ID),
catch((
prove_once(Goal, Return),
unset_alarm(ID))
, Exception, (
(Exception == timeout(ID) ->
Return = timeout
;
unset_alarm(ID),
throw(Exception)
))).
prove_once(Goal, success):-
once(Goal), !.
prove_once(_Goal, failure).
timer_start(Name):-
\+ ground(Name),
throw(error(instantiation_error, 'Timer name needs to be instantiated.')).
timer_start(Name):-
'$timer'(Name, _, _),
throw(error(permission_error(create, timer, timer_start(Name)), 'Timer already exists.')).
timer_start(Name):-
statistics(walltime, [StartTime, _]),
assertz('$timer'(Name, running, StartTime)).
timer_restart(Name):-
\+ ground(Name),
throw(error(instantiation_error, 'Timer name needs to be instantiated.')).
timer_restart(Name):-
\+ '$timer'(Name, _, _), !,
statistics(walltime, [StartTime, _]),
assertz('$timer'(Name, running, StartTime)).
timer_restart(Name):-
retract('$timer'(Name, running, _)), !,
statistics(walltime, [StartTime, _]),
assertz('$timer'(Name, running, StartTime)).
timer_restart(Name):-
retract('$timer'(Name, paused, Duration)),
statistics(walltime, [StartTime, _]),
Elapsed is StartTime - Duration,
assertz('$timer'(Name, running, Elapsed)).
timer_stop(Name, Elapsed):-
\+ '$timer'(Name, _, _),
throw(error(existence_error(timer, timer_stop(Name, Elapsed)), 'Timer does not exist.')).
timer_stop(Name, Elapsed):-
retract('$timer'(Name, running, StartTime)), !,
statistics(walltime, [EndTime, _]),
Elapsed is EndTime - StartTime.
timer_stop(Name, Elapsed):-
retract('$timer'(Name, paused, Elapsed)).
timer_elapsed(Name, Elapsed):-
\+ '$timer'(Name, _, _),
throw(error(existence_error(timer, timer_elapsed(Name, Elapsed)), 'Timer does not exist.')).
timer_elapsed(Name, Elapsed):-
'$timer'(Name, running, StartTime), !,
statistics(walltime, [EndTime, _]),
Elapsed is EndTime - StartTime.
timer_elapsed(Name, Elapsed):-
'$timer'(Name, paused, Elapsed).
timer_pause(Name, Elapsed):-
\+ '$timer'(Name, _, _),
throw(error(existence_error(timer, timer_pause(Name, Elapsed)), 'Timer does not exist.')).
timer_pause(Name, Elapsed):-
'$timer'(Name, paused, _),
throw(error(permission_error(timer, timer_pause(Name, Elapsed)), 'Timer already paused.')).
timer_pause(Name, Elapsed):-
retract('$timer'(Name, _, StartTime)),
statistics(walltime, [EndTime, _]),
Elapsed is EndTime - StartTime,
assertz('$timer'(Name, paused, Elapsed)).