Initial version of VNS algorithm

Gemfile

@@ -65,3 +65,5 @@ end
 
 gem "money"
 gem 'acts-as-taggable-on'
+
+gem "vns", path: "../vns"

Gemfile.lock

@@ -1,3 +1,9 @@
+PATH
+  remote: ../vns
+  specs:
+    vns (0.4.0.pre.rc.1)
+      activesupport
+
 GEM
   remote: https://rubygems.org/
   specs:
@@ -276,6 +282,7 @@ DEPENDENCIES
   stimulus-rails
   turbo-rails
   tzinfo-data
+  vns!
   web-console
 
 RUBY VERSION

app/services/tables/distribution.rb

@@ -0,0 +1,44 @@
+module Tables
+  class Distribution
+    attr_reader :tables
+
+    def initialize(min_per_table:, max_per_table:)
+      @min_per_table = min_per_table
+      @max_per_table = max_per_table
+    end
+
+    def random_distribution(people)
+      @tables = []
+
+      @tables << people.slice!(0..rand(@min_per_table..@max_per_table)) while people.any?
+    end
+
+    def discomfort
+      @tables.map do |table|
+        local_discomfort(table)
+      end.sum
+    end
+
+    def inspect
+      "#{@tables.count} tables, discomfort: #{discomfort}"
+    end
+
+    def pretty_print
+      @tables.map.with_index do |table, i|
+        "Table #{i + 1} (#{table.count} ppl): (#{local_discomfort(table)}) #{table.map(&:full_name).join(', ')}"
+      end.join("\n")
+    end
+
+    private
+
+    def local_discomfort(table)
+      10 * (number_of_groups(table) - 1)
+    end
+
+    def number_of_groups(table)
+      table.map do |person|
+        person.affinity_groups
+      end.flatten.uniq.count
+    end
+  end
+end

app/services/tables/swap.rb

@@ -0,0 +1,28 @@
+module Tables
+  class Swap
+    private attr_reader :initial_solution
+    def initialize(initial_solution)
+      @initial_solution = initial_solution
+    end
+
+    def each
+      @initial_solution.tables.combination(2) do |table_a, table_b|
+        table_a.product(table_b).each do |(person_a, person_b)|
+          table_a.delete(person_a)
+          table_b.delete(person_b)
+
+          table_a << person_b
+          table_b << person_a
+
+          yield(@initial_solution)
+        ensure
+          table_a.delete(person_b)
+          table_b.delete(person_a)
+
+          table_a << person_a
+          table_b << person_b
+        end
+      end
+    end
+  end
+end

db/seeds.rb

@@ -1,12 +1,4 @@
-# This file should ensure the existence of records required to run the application in every environment (production,
+NUMBER_OF_GUESTS = 50
-# development, test). The code here should be idempotent so that it can be executed at any point in every environment.
-# The data can then be loaded with the bin/rails db:seed command (or created alongside the database with db:setup).
-#
-# Example:
-#
-#   ["Action", "Comedy", "Drama", "Horror"].each do |genre_name|
-#     MovieGenre.find_or_create_by!(name: genre_name)
-#   end
 
 Expense.delete_all
 Guest.delete_all
@@ -28,10 +20,6 @@ Expense.create!(name: 'Transportation', amount: 3000, pricing_type: 'fixed')
 Expense.create!(name: 'Invitations', amount: 200, pricing_type: 'fixed')
 Expense.create!(name: 'Cake', amount: 500, pricing_type: 'fixed')
 
-<<<<<<< HEAD
-
-=======
->>>>>>> 8fd0b7c (Modify seeds file to make sure every guest is part of a group)
 samples = {
   close_family: 10,
   family_1_group_a: 5,
@@ -50,7 +38,7 @@ samples = {
   count.times { acc << affinity_group }
 end
 
-300.times do
+NUMBER_OF_GUESTS.times do
   guest = Guest.create!(first_name: Faker::Name.first_name,
                         last_name: Faker::Name.last_name,
                         email: Faker::Internet.email,

lib/tasks/vns.rake

@@ -0,0 +1,16 @@
+namespace :vns do
+  task distribute_tables: :environment do
+    engine = VNS::Engine.new
+
+    engine.add_perturbation(Tables::Swap)
+
+    initial_solution = Tables::Distribution.new(min_per_table: 8, max_per_table: 10)
+    initial_solution.random_distribution(Guest.all.shuffle)
+
+    engine.initial_solution = initial_solution
+
+    engine.target_function(&:discomfort)
+
+    best_solution = engine.run
+  end
+end