c_alarms.yap

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%%% -*- Mode: Prolog; -*-
/**
 * @file   c_alarms.yap
 * @author Theofrastos Mantadelis
 * @date   Tue Nov 17 14:50:03 2015
 * 
 * @brief  Concurrent alarms
 * 
*/
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  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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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
:- set_alarm/3unset_alarm/1time_out_call_once/3timer_start/1timer_restart/1timer_stop/2timer_elapsed/2timer_pause/2module(c_alarms, [,
                     ,
                     ,
                     ,
                     ,
                     ,
                     ,
                     ]).
 
/** @defgroup c_alarms Concurrent Alarms
@ingroup YAPLibrary
@{
 
This library provides a concurrent signals.  To use it use:
`:-use_module(library(c_alarms))`.
*/
 
 
:- member/2memberchk/2delete/3use_module(library(lists), [, , ]).
:- ord_add_element/3use_module(library(ordsets), []).
:- maplist/3use_module(library(apply_macros), []).
 
:- '$timer'/3dynamic().
 
:- meta_predicate(set_alarm(+, 0, -)).
:- meta_predicate(time_out_call_once(+, 0, -)).
:- meta_predicate(prove_once(0)).
 
:- initialization(local_init).
 
initialization:-
  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), get_next_identity,
  bb_put(alarms, [alarm(Seconds, ID, Execute)]),
  alarm(Seconds, alarm_handler, _).
 
%% @pred 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.
%
set_alarm(Seconds, Execute, ID):-
  get_next_identity(ID), get_next_identity,
  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.
 
%% @pred unset_alarm(+ID)
%
%   It will unschedule the alarm.
%   It will not affect other concurrent alarms.
%
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, _)
  ;
    alarm
  ).
 
delete_alarm(Alarms, ID, NewAlarms):-
  memberchk(alarm(Seconds, ID, Execute), Alarms),
  delete(Alarms, alarm(Seconds, ID, Execute), NewAlarms).
 
delete:-
  bb_get(alarms, [alarm(_, _, CurrentExecute)|[]]),
  bb_put(alarms, []),
  call(CurrentExecute).
call:-
  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, _)
  ;
    alarm
  ),
  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(+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.
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), once.
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):-
  \+ '$timer'(Name, _, _), '$timer',
  statistics(walltime, [StartTime, _]),
  assertz('$timer'(Name, running, StartTime)).
timer_restart(Name):-
  retract('$timer'(Name, running, _)), retract,
  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)), retract,
  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), '$timer',
  statistics(walltime, [EndTime, _]),
  Elapsed is EndTime - StartTime.
timer_elapsed(Name, Elapsed):-
  '$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)).
 
/**
@}
*/