Peterson's Process Control Algorithm Implementation in Ruby

peterson.rb

(@flag ||= []) << false << false # Initialize @flag[0] and @flag[1] as false
@shared = 0 and @turn # Initialize @shared variable and declare @turn variable

puts "---------- Peterson's Algorithm Implementation ----------"
puts "A process control algorithm to ensure that only one"
puts "process can be in the critical section at any given time."
puts ""
puts "Project Implemented in Ruby by: Raven G. Duran BSIT 2R5"
puts "---------------------------------------------------------",""

puts "Shared critical variable value: #{@shared}",""

a = Thread.fork do
  @flag[0] = true
  @turn = 1
  while @flag[1] == true and @turn == 1 
    # Busy wait
    puts "A is waiting"
    sleep 0.5
  end 

  #Critical Section
  puts "Process A has entered the critical section!"
  sleep 5 # Simulate that A is doing a task on critical section
  @shared += 1
  
  # Leave Critical Section
  puts "Process A has leaved the critical section!"
  @flag[0] = false
end

b = Thread.fork do
  @flag[1] = true
  @turn = 2
  while @flag[0] == true and @turn == 2
    # Busy wait
    puts "Process B is waiting. (Process A is currently in the critical section)"
    sleep 0.5
  end
  @shared += 1
  puts "Process B has entered the critical section!"
  sleep 1 # Simulate that B is doing a task on critical section

  # Leave Critical Section
  puts "Process B has leaved the critical section!"
  sleep 0.5
  @flag[1] = false
end

# Sync the threads
a.join
b.join

puts ""
puts "The value of shared critical variable is now: #{@shared}"

puts "","(Press anything to exit)"
gets