yap-6.3/packages/ProbLog/problog/sampling.yap

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%  $Date: 2010-12-02 15:20:15 +0100 (Thu, 02 Dec 2010) $
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%  ProbLog was developed at Katholieke Universiteit Leuven
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%  Theofrastos Mantadelis
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:- module(sampling, [problog_random/1,
                     problog_convergence_check/6]).

:- use_module(flags, _, [problog_define_flag/5,
                         problog_flag/2]).

:- use_module(os, _, [convert_filename_to_working_path/2]).

:- use_module(library(random)).

:- initialization((
  problog_define_flag(mc_batchsize, problog_flag_validate_posint, 'number of samples before update in montecarlo', 1000, monte_carlo_sampling),
  problog_define_flag(min_mc_samples, problog_flag_validate_nonegint, 'minimum number of samples before to converge', 0, monte_carlo_sampling),
  problog_define_flag(max_mc_samples, problog_flag_validate_nonegint, 'maximum number of samples waiting to converge', 1000000, monte_carlo_sampling),
  problog_define_flag(randomizer, problog_flag_validate_in_list([repeatable, nonrepeatable]), 'whether the random numbers are repeatable or not', repeatable, monte_carlo_sampling)
 )).

problog_convergence_check(Time, P, SamplesSoFar, Delta, Epsilon, Converged):-
  Epsilon is 2.0 * sqrt(P * abs(1.0 - P) / SamplesSoFar),
  (problog_flag(verbose, true) ->
    Pl is P - Epsilon,
    Ph is P + Epsilon,
    Diff is 2.0 * Epsilon,
    (problog_flag(verbose,true) ->
      format(user, '~n~w samples over ~q ms~nestimated probability ~w~n95 percent confidence interval [~w,~w]~n', [SamplesSoFar, Time, P, Pl, Ph])
    ;
      true
    ),

    % this should be generalized with log file system
    problog_flag(mc_logfile, File1),
    convert_filename_to_working_path(File1, File),
    open(File, append, Log),
    format(Log,'~w  ~8f  ~8f  ~8f  ~8f  ~3f~n',[SamplesSoFar,P,Pl,Ph,Diff,Time]),
    close(Log)


  ;
    true
  ),
  (Delta > 2.0 * Epsilon ->
    problog_flag(min_mc_samples, MinSamples),
    (MinSamples =< SamplesSoFar ->
      Converged = true
    ;
      Converged = continue
    )
  ;
    problog_flag(max_mc_samples, MaxSamples),
    (MaxSamples =< SamplesSoFar ->
      Converged = terminate
    ;
      Converged = false
    )
  ).

problog_random(Random):-
  (problog_flag(randomizer, repeatable) ->
    random(Random)
  ;
    Random is random
  ).