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# encoding=utf8 |
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import random |
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import numpy |
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from NiaPy.benchmarks.utility import Utility |
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__all__ = ['ParticleSwarmAlgorithm'] |
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class ParticleSwarmAlgorithm(object): |
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r"""Implementation of Particle Swarm Optimization algorithm. |
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**Algorithm:** Particle Swarm Optimization algorithm |
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**Date:** 2018 |
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**Author:** Lucija Brezočnik, Grega Vrbančič, and Iztok Fister Jr. |
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**License:** MIT |
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**Reference paper:** |
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Kennedy, J. and Eberhart, R. "Particle Swarm Optimization". |
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Proceedings of IEEE International Conference on Neural Networks. |
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IV. pp. 1942--1948, 1995. |
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""" |
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def __init__(self, D, NP, nFES, C1, C2, w, vMin, vMax, benchmark): |
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r"""**__init__(self, NP, D, nFES, C1, C2, w, vMin, vMax, benchmark)**. |
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Arguments: |
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NP {integer} -- population size |
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D {integer} -- dimension of problem |
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nFES {integer} -- number of function evaluations |
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C1 {decimal} -- cognitive component |
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C2 {decimal} -- social component |
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w {decimal} -- inertia weight |
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vMin {decimal} -- minimal velocity |
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vMax {decimal} -- maximal velocity |
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benchmark {object} -- benchmark implementation object |
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""" |
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self.benchmark = Utility().get_benchmark(benchmark) |
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self.NP = NP # population size; number of search agents |
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self.D = D # dimension of the problem |
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self.C1 = C1 # cognitive component |
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self.C2 = C2 # social component |
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self.w = w # inertia weight |
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self.vMin = vMin # minimal velocity |
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self.vMax = vMax # maximal velocity |
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self.Lower = self.benchmark.Lower # lower bound |
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self.Upper = self.benchmark.Upper # upper bound |
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self.nFES = nFES # number of function evaluations |
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self.eval_flag = True # evaluations flag |
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self.evaluations = 0 # evaluations counter |
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self.Fun = self.benchmark.function() |
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self.Solution = numpy.zeros((self.NP, self.D)) # positions of search agents |
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self.Velocity = numpy.zeros((self.NP, self.D)) # velocities of search agents |
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self.pBestFitness = numpy.zeros(self.NP) # personal best fitness |
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self.pBestFitness.fill(float("inf")) |
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self.pBestSolution = numpy.zeros((self.NP, self.D)) # personal best solution |
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self.gBestFitness = float("inf") # global best fitness |
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self.gBestSolution = numpy.zeros(self.D) # global best solution |
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def init(self): |
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"""Initialize positions.""" |
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for i in range(self.NP): |
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for j in range(self.D): |
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self.Solution[i][j] = random.random() * \ |
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(self.Upper - self.Lower) + self.Lower |
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def eval_true(self): |
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"""Check evaluations.""" |
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if self.evaluations == self.nFES: |
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self.eval_flag = False |
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def bounds(self, position): |
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for i in range(self.D): |
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if position[i] < self.Lower: |
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position[i] = self.Lower |
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if position[i] > self.Upper: |
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position[i] = self.Upper |
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return position |
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def move_particles(self): |
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self.init() |
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while self.eval_flag is not False: |
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for i in range(self.NP): |
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self.Solution[i] = self.bounds(self.Solution[i]) |
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self.eval_true() |
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if self.eval_flag is not True: |
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break |
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Fit = self.Fun(self.D, self.Solution[i]) |
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self.evaluations = self.evaluations + 1 |
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if Fit < self.pBestFitness[i]: |
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self.pBestFitness[i] = Fit |
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self.pBestSolution[i] = self.Solution[i] |
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if Fit < self.gBestFitness: |
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self.gBestFitness = Fit |
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self.gBestSolution = self.Solution[i] |
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for i in range(self.NP): |
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for j in range(self.D): |
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self.Velocity[i][j] = (self.w * self.Velocity[i][j]) + \ |
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(self.C1 * random.random() * (self.pBestSolution[i][j] - self.Solution[i][j])) + \ |
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(self.C2 * random.random() * (self.gBestSolution[j] - self.Solution[i][j])) |
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if self.Velocity[i][j] < self.vMin: |
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self.Velocity[i][j] = self.vMin |
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if self.Velocity[i][j] > self.vMax: |
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self.Velocity[i][j] = self.vMax |
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self.Solution[i][j] = self.Solution[i][j] + \ |
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self.Velocity[i][j] |
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return self.gBestFitness |
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def run(self): |
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return self.move_particles() |
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NiaOrg /
NiaPy
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