gistfile1.txt

# An example implementation of caching
# WARNING: this implementation does not feature any pruning/expiration strategy,
# be careful not to create a memory leak

require 'thread'

module Cacheable
  @global_cache = {}
  @mutex        = Mutex.new

  class << self
    attr_reader :global_cache
    attr_reader :mutex
  end

  def cached(key)
    value = cache_read(key)
    unless value then
      value = yield
      cache_write(key, value)
    end
    value
  end

  def cache_write(key, value)
    Cacheable.mutex.synchronize do
      Cacheable.global_cache[key] = value
    end
  end

  def cache_read(key)
    Cacheable.mutex.synchronize do
      Cacheable.global_cache[key]
    end
  end
end

class CacheDemo
  include Cacheable

  # a slow and uncached implementation of fibonacchi
  def uncached_fib(n)
    return n if n < 2

    uncached_fib(n-2)+uncached_fib(n-1)
  end

  # a slow but cached implementation of fibonacchi
  def fib(n)
    return n if n < 2

    cached("CacheDemo\#fib#{n}") do
      fib(n-2)+fib(n-1)
    end
  end
end

calc_fib = CacheDemo.new
start = Time.now
puts "Result: #{calc_fib.uncached_fib(30)}"
stop = Time.now
printf "Uncached: %.1fms\n", (stop-start)*1000

start = Time.now
puts "Result: #{calc_fib.fib(30)}"
stop = Time.now
printf "First time: %.1fms\n", (stop-start)*1000

start = Time.now
puts "Result: #{calc_fib.fib(30)}"
stop = Time.now
printf "Second time: %.1fms\n", (stop-start)*1000