"""Iterated Local Search Algorithm implementation using surrogate as fitness approximation """ # main imports import os import logging import joblib # module imports from macop.algorithms.Algorithm import Algorithm from .LSSurrogate import LocalSearchSurrogate from sklearn.linear_model import (LinearRegression, Lasso, Lars, LassoLars, LassoCV, ElasticNet) from wsao.sao.problems.nd3dproblem import ND3DProblem from wsao.sao.surrogates.walsh import WalshSurrogate from wsao.sao.algos.fitter import FitterAlgo from wsao.sao.utils.analysis import SamplerAnalysis, FitterAnalysis, OptimizerAnalysis class ILSSurrogate(Algorithm): """Iterated Local Search used to avoid local optima and increave EvE (Exploration vs Exploitation) compromise using surrogate Attributes: initalizer: {function} -- basic function strategy to initialize solution evaluator: {function} -- basic function in order to obtained fitness (mono or multiple objectives) operators: {[Operator]} -- list of operator to use when launching algorithm policy: {Policy} -- Policy class implementation strategy to select operators validator: {function} -- basic function to check if solution is valid or not under some constraints maximise: {bool} -- specify kind of optimization problem currentSolution: {Solution} -- current solution managed for current evaluation bestSolution: {Solution} -- best solution found so far during running algorithm ls_iteration: {int} -- number of evaluation for each local search algorithm surrogate_file: {str} -- Surrogate model file to load (model trained using https://gitlab.com/florianlprt/wsao) start_train_surrogate: {int} -- number of evaluation expected before start training and use surrogate surrogate: {Surrogate} -- Surrogate model instance loaded ls_train_surrogate: {int} -- Specify if we need to retrain our surrogate model (every Local Search) solutions_file: {str} -- Path where real evaluated solutions are saved in order to train surrogate again callbacks: {[Callback]} -- list of Callback class implementation to do some instructions every number of evaluations and `load` when initializing algorithm """ def __init__(self, _initalizer, _evaluator, _operators, _policy, _validator, _surrogate_file_path, _start_train_surrogate, _ls_train_surrogate, _solutions_file, _maximise=True, _parent=None): # set real evaluator as default super().__init__(_initalizer, _evaluator, _operators, _policy, _validator, _maximise, _parent) self.n_local_search = 0 self.surrogate_file_path = _surrogate_file_path self.start_train_surrogate = _start_train_surrogate self.surrogate_evaluator = None self.ls_train_surrogate = _ls_train_surrogate self.solutions_file = _solutions_file def train_surrogate(self): """etrain if necessary the whole surrogate fitness approximation function """ # Following https://gitlab.com/florianlprt/wsao, we re-train the model # --------------------------------------------------------------------------- # cli_restart.py problem=nd3d,size=30,filename="data/statistics_extended_svdn" \ # model=lasso,alpha=1e-5 \ # surrogate=walsh,order=3 \ # algo=fitter,algo_restarts=10,samplefile=stats_extended.csv \ # sample=1000,step=10 \ # analysis=fitter,logfile=out_fit.csv problem = ND3DProblem(size=len(self.bestSolution.data)) # problem size based on best solution size (need to improve...) model = Lasso(alpha=1e-5) surrogate = WalshSurrogate(order=3, size=problem.size, model=model) analysis = FitterAnalysis(logfile="train_surrogate.log", problem=problem) algo = FitterAlgo(problem=problem, surrogate=surrogate, analysis=analysis, seed=problem.seed) print("Start fitting again the surrogate model") for r in range(10): print("Iteration n°{0}: for fitting surrogate".format(r)) algo.run(samplefile=self.solutions_file, sample=100, step=10) joblib.dump(algo, self.surrogate_file_path) def load_surrogate(self): """Load algorithm with surrogate model and create lambda evaluator function """ # need to first train surrogate if not exist if not os.path.exists(self.surrogate_file_path): self.train_surrogate() self.surrogate = joblib.load(self.surrogate_file_path) # update evaluator function self.surrogate_evaluator = lambda s: self.surrogate.surrogate.predict([s.data])[0] def add_to_surrogate(self, solution): # save real evaluated solution into specific file for surrogate with open(self.solutions_file, 'a') as f: line = "" for index, e in enumerate(solution.data): line += str(e) if index < len(solution.data) - 1: line += "," line += ";" line += str(solution.score) f.write(line + "\n") def run(self, _evaluations, _ls_evaluations=100): """ Run the iterated local search algorithm using local search (EvE compromise) Args: _evaluations: {int} -- number of global evaluations for ILS _ls_evaluations: {int} -- number of Local search evaluations (default: 100) Returns: {Solution} -- best solution found """ # by default use of mother method to initialize variables super().run(_evaluations) # enable resuming for ILS self.resume() # initialize current solution self.initRun() if self.start_train_surrogate > self.getGlobalEvaluation(): # get `self.start_train_surrogate` number of real evaluations and save it into surrogate dataset file # using randomly generated solutions (in order to cover seearch space) while self.start_train_surrogate > self.getGlobalEvaluation(): newSolution = self.initializer() # evaluate new solution newSolution.evaluate(self.evaluator) # add it to surrogate pool self.add_to_surrogate(newSolution) self.increaseEvaluation() # train surrogate on real evaluated solutions file self.train_surrogate() self.load_surrogate() # local search algorithm implementation while not self.stop(): # set current evaluator based on used or not of surrogate function current_evaluator = self.surrogate_evaluator if self.start_train_surrogate < self.getGlobalEvaluation() else self.evaluator # create new local search instance # passing global evaluation param from ILS ls = LocalSearchSurrogate(self.initializer, current_evaluator, self.operators, self.policy, self.validator, self.maximise, _parent=self) # add same callbacks for callback in self.callbacks: ls.addCallback(callback) # create and search solution from local search newSolution = ls.run(_ls_evaluations) # if better solution than currently, replace it (solution saved in training pool, only if surrogate process is in a second process step) if self.isBetter(newSolution) and self.start_train_surrogate < self.getGlobalEvaluation(): # if better solution found from local search, retrained the found solution and test again # without use of surrogate fitness_score = self.evaluator(newSolution) self.increaseEvaluation() newSolution.score = fitness_score # if solution is really better after real evaluation, then we replace if self.isBetter(newSolution): self.bestSolution = newSolution self.add_to_surrogate(newSolution) # check if necessary or not to train again surrogate if self.n_local_search % self.ls_train_surrogate == 0 and self.start_train_surrogate < self.getGlobalEvaluation(): # train again surrogate on real evaluated solutions file self.train_surrogate() # reload new surrogate function self.load_surrogate() # increase number of local search done self.n_local_search += 1 self.information() logging.info("End of %s, best solution found %s" % (type(self).__name__, self.bestSolution)) self.end() return self.bestSolution