fixture_generator.rb

require 'benchmark'
require 'pp'

def build_fixtures(n_teams, play_each_other=1)
  teams = (1..n_teams).to_a
  n_rounds = n_teams - 1 + n_teams%2
  fixtures_per_round = n_teams / 2
  # puts "Teams     : #{teams.inspect}"
  # puts "Rounds    : #{n_rounds}"
  # puts "Games per : #{fixtures_per_round}"

  bottom = teams.pop(n_teams/2)
  key = bottom.pop
  top = teams.reverse
  
  set = (0..(n_rounds-1)).map do |round|
    top.push(bottom.pop)
    bottom.unshift(top.shift)
    # puts "--"
    # puts "(#{top*','})"
    # puts "(#{bottom*','})#{key}"
    # puts "--"
    (0..(fixtures_per_round-1)).map do |f|
      round%2==0 ? [top[f], bottom[f]||key] : [bottom[f]||key, top[f]]
    end
  end
  
  if play_each_other > 1
    reverse_set = set.map { |x| x.map { |y| y.reverse }}
    (1..play_each_other).inject([]) do |rounds, l|
      rounds += (l%2==0 ? set : reverse_set )
    end
  else
    set
  end
end

final = []

Benchmark.bm do |x|
  x.report("5 teams")  { (1..10000).each { |n| final = build_fixtures(5) } }
  x.report("5 teams (2x)")  { (1..10000).each { |n| final = build_fixtures(5,2) } }
  x.report("10 teams") { (1..10000).each { |n| final = build_fixtures(10) } }
  x.report("10 teams (4x)") { (1..10000).each { |n| final = build_fixtures(10,4) } }
  x.report("15 teams") { (1..10000).each { |n| final = build_fixtures(15) } }
  x.report("20 teams") { (1..10000).each { |n| final = build_fixtures(20) } }
  x.report("25 teams") { (1..10000).each { |n| final = build_fixtures(25) } }
end

final

puts "--"
pp build_fixtures(4,2)