From 405e698a6f016f9a36c5ae4e75d71e629dec78c6 Mon Sep 17 00:00:00 2001
From: Manuel Bustillo <bustikiller@bustikiller.com>
Date: Wed, 24 Jul 2024 20:14:58 +0200
Subject: [PATCH] Initial version of VNS algorithm

---
 Gemfile                             |  4 ++-
 Gemfile.lock                        |  7 +++++
 app/services/tables/distribution.rb | 44 +++++++++++++++++++++++++++++
 app/services/tables/swap.rb         | 28 ++++++++++++++++++
 db/seeds.rb                         | 16 ++---------
 lib/tasks/vns.rake                  | 16 +++++++++++
 6 files changed, 100 insertions(+), 15 deletions(-)
 create mode 100644 app/services/tables/distribution.rb
 create mode 100644 app/services/tables/swap.rb
 create mode 100644 lib/tasks/vns.rake

diff --git a/Gemfile b/Gemfile
index a3cbafd..7ff1257 100644
--- a/Gemfile
+++ b/Gemfile
@@ -64,4 +64,6 @@ group :development do
 end
 
 gem "money"
-gem 'acts-as-taggable-on'
\ No newline at end of file
+gem 'acts-as-taggable-on'
+
+gem "vns", path: "../vns"
\ No newline at end of file
diff --git a/Gemfile.lock b/Gemfile.lock
index 6f951a1..8d5808f 100644
--- a/Gemfile.lock
+++ b/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
diff --git a/app/services/tables/distribution.rb b/app/services/tables/distribution.rb
new file mode 100644
index 0000000..b8a9997
--- /dev/null
+++ b/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
diff --git a/app/services/tables/swap.rb b/app/services/tables/swap.rb
new file mode 100644
index 0000000..ddc3681
--- /dev/null
+++ b/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
diff --git a/db/seeds.rb b/db/seeds.rb
index e79ad9b..c5f684c 100644
--- a/db/seeds.rb
+++ b/db/seeds.rb
@@ -1,12 +1,4 @@
-# This file should ensure the existence of records required to run the application in every environment (production,
-# 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
+NUMBER_OF_GUESTS = 50
 
 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,
diff --git a/lib/tasks/vns.rake b/lib/tasks/vns.rake
new file mode 100644
index 0000000..dd5a942
--- /dev/null
+++ b/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