path: root/tsp.py

#!/usr/bin/env python
# coding=utf-8

'''
 Various Travelling Salesman Problem algorithms
 Author : Guillaume "iXce" Seguin
 Email  : guillaume@segu.in

 Copyright (C) 2007 Guillaume Seguin

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License
 as published by the Free Software Foundation; either version 2
 of the License, or (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin Street, Fifth Floor,
 Boston, MA  02110-1301, USA.
'''

import pygtk
pygtk.require ("2.0")
import gtk
import gobject

gtk.gdk.threads_init ()

import random
import math
import cairo
import threading
import datetime

MAX_X = 500 # Max X (virtual) coordinate
MAX_Y = 500 # Max Y (virtual) coordinate
OFFSET_X = 20 # Left & right offsets (for drawing purpose)
OFFSET_Y = 20 # Top & bottom offsets (for drawing purpose)

CITY_RADIUS = 3 # Radius of the visual city points

SHOW_NAMES = True

INIT_RANDOM = "Random"
INIT_GREEDY = "Greedy"
INIT_GREEDY_BEST = "Greedy (Best)"

INITS = [INIT_RANDOM, INIT_GREEDY, INIT_GREEDY_BEST]  # Init methods choices
ALGOS = ["2opt", "MonteCarlo", "Annealing"] # Algorithms choices 
COUNTS = [10, 25, 50, 100, 250] # City counts choices

# Default settings
DEFAULT_INIT = INIT_RANDOM
DEFAULT_ALGO = "Annealing"
DEFAULT_COUNT = 50

class Color:
    '''Helper object for color handling'''

    def __init__ (self, r, g, b):
        self.r = r
        self.g = g
        self.b = b

CITY_COLOR = Color (0.9, 0, 0) # Red
TEXT_COLOR = Color (0, 0, 0)   # Black
PATH_COLOR = Color (0, 0, 0.8) # Blue

def distance (c1, c2):
    '''Compute the distance between two points'''
    return math.sqrt ((c2.x - c1.x) ** 2 + (c2.y - c1.y) ** 2)

def draw_map (cities, cr):
    '''Draw a map of points on a Cairo context'''
    global CITY_COLOR, TEXT_COLOR, SHOW_NAMES
    def draw_point (city):
        '''Helper function to draw a point'''
        cr.arc (city.x, city.y, CITY_RADIUS, 0, 2 * math.pi)
        cr.fill ()
    def draw_name (city):
        '''Helper function to draw a point label'''
        cr.move_to (city.x + 6, city.y + 6)
        cr.show_text ("%d" % city.i)
        cr.fill ()
    cr.set_operator (cairo.OPERATOR_OVER)
    cr.set_source_rgb (CITY_COLOR.r, CITY_COLOR.g, CITY_COLOR.b)
    map (draw_point, cities.values ())
    if not SHOW_NAMES:
        return
    cr.set_source_rgb (TEXT_COLOR.r, TEXT_COLOR.g, TEXT_COLOR.b)
    map (draw_name, cities.values ())

def draw_path (cities, path, cr):
    '''Draw a path on a Cairo context'''
    global PATH_COLOR
    prev = path[0]
    list = path[1:] + [prev]
    length = 0
    cr.set_operator (cairo.OPERATOR_OVER)
    cr.set_source_rgb (PATH_COLOR.r, PATH_COLOR.g, PATH_COLOR.b)
    cr.set_line_width (1)
    cr.move_to (cities[prev].x, cities[prev].y)
    for i in list:
        cr.line_to (cities[i].x, cities[i].y)
    cr.stroke ()

class City:
    '''Helper object for points map handling'''

    i = 0
    x = 0
    y = 0

    def __init__ (self, i):
        '''Initialize object (generate random coordinates)'''
        self.i = i
        self.x = OFFSET_X + random.uniform (0, MAX_X)
        self.y = OFFSET_Y + random.uniform (0, MAX_Y)

class Path (list):
    '''Helper object that automagically computes the path length'''

    context = None

    def __init__ (self, context, list):
        '''Initalize list & object'''
        self.context = context
        for i in list:
            self.append (i)
        self.compute_length ()

    def compute_length (self):
        '''Compute length, the computation is pretty straight-forward'''
        prev = self[0]
        list = self[1:] + [prev] # Add the first element of the list to 
                                 # the end to close the path
        length = 0
        for i in list:
            length += self.context.dists[prev][i]
            prev = i
        self.length = length

class Context:
    '''Helper object handling the city map and distances computations, and
featuring some basic methods such as nearest neighbours (a.k.a. greedy)
algorithm'''

    count = 0
    dists = {}
    map = {}

    def __init__ (self, delayed = False, count = DEFAULT_COUNT):
        '''Initialize object'''
        self.count = count
        if not delayed:
            self.prepare ()

    def prepare (self):
        '''Prepare context data'''
        self.generate_map ()
        self.compute_dists ()
    
    def generate_map (self):
        '''Generate a map of random points'''
        # FIXME: maybe should we check for duplicates?
        self.map = {}
        for i in range (0, self.count):
            self.map[i] = City (i)

    def compute_dists (self):
        '''Compute the distances array'''
        self.dists = {}
        # Only compute half of the array, it's symetric
        for i in range (0, self.count):
            self.dists[i] = {}
            for j in range (i, self.count):
                self.dists[i][j] = distance (self.map[i], self.map[j])
        for i in range (0, self.count):
            for j in range (0, i):
                self.dists[i][j] = self.dists[j][i]

    def draw_to_cr (self, cr, path = None):
        '''Draw map & path (if any) to the given Cairo context'''
        if path:
            draw_path (self.map, path, cr)
        draw_map (self.map, cr)

    def draw_png (self, filename, path = None):
        '''Dump map & path (if any) to a PNG file'''
        surface = cairo.ImageSurface (cairo.FORMAT_ARGB32,
                                      MAX_X + 2 * OFFSET_X,
                                      MAX_Y + 2 * OFFSET_Y)
        cr = cairo.Context (surface)
        cr.set_operator (cairo.OPERATOR_CLEAR)
        cr.paint ()
        self.draw_to_cr (cr, path)
        surface.write_to_png (filename)

    def nearest_neighbours (self, start = 0):
        '''Nearest neighbours (a.k.a. greedy) algorithm'''
        def reduce_nearest (d1, d2):
            '''Reduce function to find the nearest point of a list'''
            if d1[1] < d2[1]: return d1
            else: return d2
        path = [start]
        while len (path) < len (self.map):
            current = path[-1]
            dists = self.dists[current].items ()
            dists = filter (lambda (i, dist): i not in path, dists)
            next = reduce (reduce_nearest, dists)
            path.append (next[0])
        return Path (self, path)

    def nearest_neighbours_best (self):
        '''Nearest neighbours algorithm applied to each city of the list'''
        best = None
        for i in self.map.keys ():
            path = self.nearest_neighbours (start = i)
            if not best or path.length < best.length:
                best = path
        return best

    def random_path (self):
        '''Random path generator'''
        path = range (0, self.count)
        random.shuffle (path)
        return Path (self, path)

'''
A few notes about the way algorithms should be implemented:
* The class name should look like "Algo_Name" where Name is the name that will
be displayed in the GUI
* The "run" method is what will be run by the running thread
* The "run" method must use the "yield" mechanism to raise the current path as
it goes on. This lets the running thread nicely interrupt execution if needed,
and lets it quickly halt.
'''

class Algo:
    '''Base class for algorithm, please extend me!'''

    context = None
    need_init = True

    def __init__ (self, context):
        '''Initialize object'''
        self.context = context

    def run (self):
        '''Implement this in your algorithm subclass'''

class Algo_2opt (Algo):
    '''Classic 2opt algorithm'''

    def run (self, path = None):
        '''Algorithm main loop'''
        if not path:
            path = self.context.nearest_neighbours_best ()
        best = path
        while True:
            yield path
            path = self.do_2opt (best)
            if path.length < best.length:
                best = path

    def do_2opt (self, path):
        '''Do a simple transformation: given two points i and j, reverse the
path between i and j (e.g. [0, 1, 2, 3, 4, 5] with i = 1 and j = 4 becomes
[0, 1, 3, 2, 4, 5]. This is better than just exchanging two points because the
former only breaks 2 links while the latters breaks 4.'''
        i, j = random.sample (path, 2)
        if i < j:
            segment = path[i + 1:j]
            segment.reverse ()
            return Path (self.context, path[:i + 1] + segment + path[j:])
        else:
            '''If i > j, loop around the list'''
            segment = path[i + 1:] + path[:j]
            segment.reverse ()
            return Path (self.context, path[j:i + 1] + segment)

class Algo_Annealing (Algo_2opt):
    '''Simulated annealing algorithm'''

    t0      = 10.0 # Initial temperature
    updates = 0    # Accepted updates counter

    def run (self, path = None):
        '''Algorithm main loop'''
        self.t0 = min (self.t0, self.t0 * self.context.count / 50)
        self.updates = 0
        if not path:
            path = self.context.nearest_neighbours_best ()
        current = best = path
        while True:
            yield current
            next = self.do_2opt (current)
            if next.length < best.length:
                current = best = next
                self.updates += 1
            elif next.length <= current.length \
              or self.accept_change (current, next):
                current = next
                self.updates += 1

    def accept_change (self, current, next):
        '''Choose if a worse path is accepted anyway, this is the key of the
simulated annealing algorithm: the path will be accepted if the result of
exp (- (next length - current length) / temperature) is greater than a random
floating point number, where temperature evolves according to a given law
based on the current number of iterations (or so)'''
        delta = next.length - current.length
        p0 = random.random ()
        t0 = 1
        p = math.exp (- delta / self.temp ())
        if p0 <= p:
            return True
        else:
            return False

    def temp (self):
        '''Temperature law: t = t0 - accepted_updates * 0.001 (min'd to 0.1)'''
        return max (self.t0 - self.updates * 0.001, 0.1)

class Algo_MonteCarlo (Algo_2opt):
    '''2opt-based algorithm with Monte-Carlo perturbations'''

    unsuccessful_loops      = 0
    MAX_UNSUCCESSFUL_LOOPS  = 1000

    def run (self, path = None):
        '''Algorithm main loop'''
        if not path:
            path = self.context.nearest_neighbours_best ()
        current = path
        while True:
            yield path
            path = self.do_2opt (current)
            if path.length < current.length:
                current = path
                self.unsuccessful_loops = 0
            else:
                '''If we did not find a better result, increment this'''
                self.unsuccessful_loops += 1
            '''After MAX_UNSUCCESSFUL_LOOPS, perturbate the current path'''
            if self.unsuccessful_loops > self.MAX_UNSUCCESSFUL_LOOPS:
                path = current = self.perturbate (current)
                self.unsuccessful_loops = 0

    def perturbate (self, path):
        '''Perturbate a path by exchanging two points'''
        i, j = random.sample (xrange (len (path)), 2)
        path[j], path[i] = path[i], path[j]
        return Path (self.context, path)

class AlgoThread (threading.Thread):
    '''Threading running a given algorithm'''

    context   = None
    algo      = None
    gui       = None
    canvas    = None
    init      = False
    terminate = False
    time      = None

    runner    = None
    best      = None

    def __init__ (self, context, algo, gui, canvas, init = None):
        '''Initialize the thread'''
        threading.Thread.__init__ (self)
        self.context = context
        self.algo = algo
        self.gui = gui
        self.canvas = canvas
        self.init = init

    def update_best (self, path, time):
        '''Update GUI to reflect the finding of a better solution'''
        gtk.gdk.threads_enter ()
        if not path: length = None
        else: length = path.length
        self.gui.update_best (length, time)
        self.canvas.redraw (path = path, damage = True)
        gtk.gdk.threads_leave ()

    def run (self):
        '''Main thread loop: generate a path (randomly or not, according to
the current settings) and run the algorithm on it until the stop () function
is called.'''
        start = datetime.datetime.now ()
        if not self.runner:
            self.time = datetime.timedelta ()
            self.update_best (path = None, time = None)
            if self.algo.need_init:
                if self.init == INIT_GREEDY_BEST:
                    for i in self.context.map:
                        if self.terminate:
                            self.time = self.time + self.get_time (start)
                        path = self.context.nearest_neighbours (start = i)
                        if not best or path.length < best.length:
                            self.best = path
                elif self.init == INIT_GREEDY:
                    self.best = self.context.nearest_neighbours ()
                else:
                    self.best = self.context.random_path ()
                self.update_best (path = self.best,
                                  time = self.get_time (start))
                self.runner = self.algo.run (self.best)
            else:
                self.runner = self.algo.run ()
        while not self.terminate:
            path = self.runner.next ()
            if not self.best or path.length < self.best.length:
                self.best = path
                self.update_best (path = self.best,
                                  time = self.get_time (start))
        self.time = self.time + self.get_time (start)

    def get_time (self, start):
        '''Return timedelta since a given date'''
        return self.time + datetime.datetime.now () - start

    def resume (self):
        '''Resume thread: since we can't start a Thread twice, let's copy
its data into a new Thread, start the new one and return it'''
        thread = AlgoThread (self.context, self.algo, self.gui, self.canvas,
                             self.init)
        thread.runner = self.runner
        thread.best = self.best
        thread.time = self.time
        thread.start ()
        return thread

    def stop (self):
        '''Stop thread'''
        self.terminate = True

class AlgoCanvas (gtk.DrawingArea):
    '''Canvas widget for displaying maps & paths'''

    context = None
    surface = None
    path    = None

    def __init__ (self, context):
        '''Initialize widget'''
        gtk.DrawingArea.__init__ (self)
        self.context = context
        self.connect ("expose-event", self.expose)
        self.set_size_request (MAX_X + 2 * OFFSET_X, MAX_Y + 2 * OFFSET_Y)

    def redraw (self, path = None, damage = False):
        '''Redraw surface using the given path (if any)'''
        self.path = path
        self.surface = cairo.ImageSurface (cairo.FORMAT_ARGB32,
                                           MAX_X + 2 * OFFSET_X,
                                           MAX_Y + 2 * OFFSET_Y)
        cr = cairo.Context (self.surface)
        cr.set_operator (cairo.OPERATOR_CLEAR)
        cr.paint ()
        self.context.draw_to_cr (cr, self.path)
        if damage:
            '''Damage widget if requested'''
            self.queue_draw ()

    def expose (self, widget, event):
        '''Handle expose events: copy the saved surface to the new widget
Cairo context, clipping the draw area if needed'''
        cr = self.window.cairo_create ()
        if not self.surface:
            self.redraw ()
        cr.set_source_surface (self.surface)
        cr.rectangle (event.area.x, event.area.y,
                      event.area.width, event.area.height)
        cr.clip ()
        cr.paint ()
        return False

class AlgoGui (gtk.Window):
    '''GUI for testing TSP algorithms'''

    context = None
    algo    = None
    thread  = None

    canvas       = None
    init_box     = None
    algo_box     = None
    count_box    = None
    gen_button   = None
    start_button = None
    stop_button  = None

    best_label   = None
    config_label = None

    def __init__ (self):
        '''Initialize GUI'''
        global INITS, ALGOS, COUNTS
        gtk.Window.__init__ (self)
        self.context = Context (delayed = True) # Prepare Context
        self.algo = None
        # GTK stuff
        self.set_title ("TSP Algorithm test GUI")
        self.set_position (gtk.WIN_POS_CENTER)
        self.connect ("delete-event", gtk.main_quit)
        box = gtk.VBox ()
        self.add (box)
        self.canvas = AlgoCanvas (self.context) # Our canvas
        alignment = gtk.Alignment (0.5, 0.5, 0, 0)
        alignment.add (self.canvas)
        box.pack_start (alignment, False, False)
        # Settings
        hbox = gtk.HBox ()
        alignment = gtk.Alignment (0.5, 0.5, 0, 0)
        alignment.add (hbox)
        box.pack_start (alignment, False, False)
        # Init methods
        self.init_box = gtk.combo_box_new_text ()
        map (self.init_box.append_text, INITS)
        self.init_box.set_active (INITS.index (DEFAULT_INIT))
        hbox.pack_start (self.init_box, False, False)
        # Algorithms
        self.algo_box = gtk.combo_box_new_text ()
        map (self.algo_box.append_text, ALGOS)
        self.algo_box.set_active (ALGOS.index (DEFAULT_ALGO))
        hbox.pack_start (self.algo_box, False, False)
        # City counts
        self.count_box = gtk.combo_box_new_text ()
        map (lambda i: self.count_box.append_text ("%d cities" % i), COUNTS)
        self.count_box.set_active (COUNTS.index (DEFAULT_COUNT))
        hbox.pack_start (self.count_box, False, False)
        # Show labels button
        names_button = gtk.CheckButton (label = "Show labels")
        names_button.connect ("toggled", self.toggle_show_names)
        names_button.set_active (True)
        hbox.pack_start (names_button, False, False)
        # Buttons
        hbox = gtk.HBox ()
        alignment = gtk.Alignment (0.5, 0.5, 0, 0)
        alignment.add (hbox)
        box.pack_start (alignment, False, False)
        # Generate button
        self.gen_button = gtk.Button ("Generate")
        self.gen_button.connect ("clicked", self.generate)
        hbox.pack_start (self.gen_button, False, False)
        # Start button
        self.start_button = gtk.Button ("Start")
        self.start_button.connect ("clicked", self.start)
        self.start_button.set_sensitive (False)
        hbox.pack_start (self.start_button, False, False)
        # Resume button
        self.resume_button = gtk.Button ("Resume")
        self.resume_button.connect ("clicked", self.resume)
        self.resume_button.set_sensitive (False)
        hbox.pack_start (self.resume_button, False, False)
        # Stop button
        self.stop_button = gtk.Button ("Stop")
        self.stop_button.connect ("clicked", self.stop)
        self.stop_button.set_sensitive (False)
        hbox.pack_start (self.stop_button, False, False)
        # Informative labels
        self.best_label = gtk.Label ()
        self.update_best (length = None, time = None)
        box.pack_start (self.best_label, False, False)
        self.config_label = gtk.Label ()
        self.update_config (config = False)
        box.pack_start (self.config_label, False, False)

    def toggle_show_names (self, button):
        '''Toggle SHOW_NAMES setting & damage canvas'''
        global SHOW_NAMES
        SHOW_NAMES = button.get_active ()
        self.canvas.redraw (path = self.canvas.path, damage = True)

    def get_count (self):
        '''Get currently selected city count'''
        count = self.count_box.get_active_text ().split (" ")[0]
        return int (count)

    def get_algo (self):
        '''Get currently selected algorithm'''
        return self.algo_box.get_active_text ()

    def get_init (self):
        '''Get currently selected init method'''
        return self.init_box.get_active_text ()

    def generate (self, *args):
        '''Generate a new map'''
        self.thread = None
        self.context.count = self.get_count ()
        self.context.prepare ()
        self.start_button.set_sensitive (True)
        self.resume_button.set_sensitive (False)
        self.canvas.redraw (damage = True)

    def start (self, *args):
        '''Run algorithm'''
        global INITS
        self.stop ()
        self.update_config ()
        self.algo = eval ("Algo_%s" % self.get_algo ()) (self.context)
        self.thread = AlgoThread (self.context, self.algo, self, self.canvas,
                                  init = self.get_init ())
        self.thread.start ()
        self.gen_button.set_sensitive (False)
        self.start_button.set_sensitive (False)
        self.resume_button.set_sensitive (False)
        self.stop_button.set_sensitive (True)

    def resume (self, *args):
        '''Resume algorithm execution'''
        if not self.thread or self.thread.isAlive ():
            return
        self.thread = self.thread.resume ()
        self.gen_button.set_sensitive (False)
        self.start_button.set_sensitive (False)
        self.resume_button.set_sensitive (False)
        self.stop_button.set_sensitive (True)

    def stop (self, *args):
        '''Halt algorithm'''
        if self.thread:
            self.thread.stop ()
            self.thread.join (0.1)
            if self.thread.isAlive ():
                gobject.timeout_add (100, self.stop)
                return
        self.gen_button.set_sensitive (True)
        self.start_button.set_sensitive (True)
        self.resume_button.set_sensitive (True)
        self.stop_button.set_sensitive (False)

    def update_best (self, length, time):
        '''Update best solution length label'''
        if not length:
            self.best_label.set_markup ("<b>Best length yet</b>: N/A")
            return
        length = round (length, 2)
        time = round (time.seconds + float (time.microseconds) / 1000000, 2)
        label = '''<b>Best length yet</b>: %s (found in %ss)'''
        self.best_label.set_markup (label % (length, time))

    def update_config (self, config = True):
        '''Update current configuration label'''
        if not config:
            self.config_label.set_markup ("<b>Configuration</b>: N/A")
            return
        config = '''<b>Configuration</b>: %d cities, using %s algorithm and \
%s init'''
        self.config_label.set_markup (config % (self.get_count (),
                                                self.get_algo (),
                                                self.get_init ()))

if __name__ == "__main__":
    gui = AlgoGui ()
    gui.show_all ()
    try:
        gtk.main ()
    except KeyboardInterrupt:
        pass
    gui.stop ()