small refactoring

README.md

@@ -121,6 +121,8 @@ a valid tour. If this new tour is shorter, make the change.
 
 ![Final solution](readme/lp_solution.png)
 
+**Note**: there is an exponentially growing number of subtour constraints, which makes this algorithm inefficient for larger instances of the TSP. One way to improve it is to use lazy constraints, i.e ignore the subtour constraints and eliminate them one by one when looking for a feasible solution.
+
 # Genetic algorithm
 
 ![Genetic algorithm](readme/genetic_algorithm.gif)

algorithms/genetic_algorithm.py

@@ -102,8 +102,7 @@ def partially_mapped_crossover(self, i1, i2):
     def fill_generation(self, generation):
         # we select 30 random elements and keep only the best 10
         if generation:
-            generation = sorted(sample(generation, 30), key=self.compute_length)
-        # generation = list(map(self.pairwise_exchange, generation[10:]))
+            generation = sorted(sample(generation, 30), key=self.compute_length)[10:]
         while len(generation) < 70:
             generation.append(self.generate_solution())
         return generation
@@ -118,8 +117,6 @@ def cycle(self, generation, **data):
             ng.extend(getattr(self, crossover)(*par) if random() < cr else par)
         # mutation step
         ng = [getattr(self, mutation)(i) for i in ng]
-        print(data)
-        print(cr, mr, mutation, crossover)
         # order the generation according to the fitness value
         ng = sorted(ng, key=self.compute_length)
         return ng, self.format_solution(ng[0]), self.compute_length(ng[0])

flask_app.py

@@ -106,7 +106,7 @@ def index():
 @app.route('/<algorithm>', methods=['POST'])
 def algorithm(algorithm):
     session['best'] = float('inf')
-    return jsonify(*getattr(tsp, algorithm)(), False)
+    return jsonify(*getattr(tsp, algorithm)())
 
 
 @socketio.on('genetic_algorithm')
@@ -116,10 +116,7 @@ def genetic_algorithm(data):
     session['generation'], best, length = tsp.cycle(session['generation'], **data)
     if length < session['best']:
         session['best'] = length
-        emit('draw', ([best], [length], True))
-    else:
-        emit('draw', ([best], [length], False))
-
+        emit('draw', ([best], [length]))
 
 if __name__ == '__main__':
     socketio.run(app)

templates/index.html

@@ -157,7 +157,7 @@
     var currentAlgorithm = undefined;
 
     function tourConstruction(algorithm){
-        clearAll();
+        clearLines(polylines);
         if (window.optimizationTimer) {
           clearTimeout(window.optimizationTimer);
           window.optimizationTimer = 0;
@@ -174,7 +174,7 @@
 
     var generationNumber = 0;
     function geneticAlgorithm() {
-      clearAll();
+      clearLines(polylines);
       // we cannot use setInterval as the timer depends on the slider
       // we have to use setTimeout for the speed to vary through time
       function timeout() {
@@ -329,27 +329,19 @@
         {% endif %}
         }
       }
-
-    // Function that clears all lines
-    function clearAll(){
-      clearLines(polylines);
-      clearLines(bestPolylines);
-      }
 
     /* Function to draw a serie of paths, with optional arguments: 
     - lengths for updating the length in real-time, if createPath is not
     called from another function like createIntermediatePath */
 
-      async function draw(paths, lengths, best){
+      async function draw(paths, lengths){
         for (j = 0; j < paths.length; j++) {
           // update the score
           if (lengths) {
             $("#score").text(Math.round(Number(lengths[j])));
             }
-          var color = best ? '#d4222a' : '#0000ff';
-          var lines = best ? bestPolylines : polylines;
-          clearLines(lines);
-
+          var color = '#0000ff';
+          clearLines(polylines);
           for (i = 0; i < paths[j].length - 1; i++) { 
 
             var source_lat = paths[j][i][0];
@@ -370,15 +362,15 @@
                 });
 
               polyline.addTo(map);
-              lines.push(polyline);
+              polylines.push(polyline);
             {% else %}
               var polygonSD = WE.polygon(
                 [[source_lat, source_lon], [destination_lat, destination_lon],
                 [source_lat, source_lon]], {color: color,opacity: 20}).addTo(earth);
               var polygonDS = WE.polygon(
                 [[destination_lat, destination_lon], [source_lat, source_lon],
                 [destination_lat, destination_lon]], {color: color,opacity: 20}).addTo(earth);
-              lines.push(polygonSD, polygonDS)
+              polylines.push(polygonSD, polygonDS)
             {% endif %}
             }
           var speed = $('#base_slider').val();