yap-6.3/library/c_alarms.yap

%%% -*- 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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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

:- 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]).

/** @defgroup c_alarms Concurrent Alarms
@ingroup library
@{

This library provides a concurrent signals.  To use it use:
`:-use_module(library(c_alarms))`.
*/


:- 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)
%
%   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), !,
  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)
%
%   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, _)
  ;
    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(+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), !.
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)).

/**
@}
*/