[英]Ruby Multithreaded producer-consumer
我不到一周前就開始使用Ruby,但是已經開始欣賞這種語言的強大功能。 我正在嘗試解決一個典型的生產者-消費者問題,該問題已實現為一棵橙樹(參見http://pine.fm/LearnToProgram/?Chapter=09 )。 橘樹每年生長直到死亡,並每年產生隨機數量的橘子(生產者)。 只要樹上有橘子(消費者),就可以采摘橘子。
我這里有兩個問題:
以下代碼為我提供了以下異常(無法附加,無選項):
\n /Users/Abhijit/Workspace/eclipse/ruby/learn_to_program/orange_tree.rb:84:\n 警告:實例變量@orange_tree未初始化\n /Users/Abhijit/Workspace/eclipse/ruby/learn_to_program/orange_tree.rb:84:in'':\n\n 來自的nil:NilClass(NoMethodError)的未定義方法'age'\n /Users/Abhijit/Workspace/eclipse/ruby/learn_to_program/orange_tree.rb:45:in`'\n
我不確定多線程部分是否正確編碼。
我自己寫了幾本書,包括“ Ruby編程”和“ Ruby編程語言”,但沒有一本書包含真正的“生產者-消費者問題”。
PS:為了全面披露,我還將這個問題發布在Ruby論壇中。 但是,我在這里看到了很好的答案和/或建議,希望我也能從中得到一些。
require 'thread'
class OrangeTree
GROWTH_PER_YEAR = 1
AGE_TO_START_PRODUCING_ORANGE = 3
AGE_TO_DIE = 7
ORANGE_COUNT_RELATIVE_TO_AGE = 50
def initialize
@height = 0
@age = 0
@orange_count = 0
end
def height
return @height
end
def age
return @age
end
def count_the_oranges
return @orange_count
end
def one_year_passes
@age += 1
@height += GROWTH_PER_YEAR
@orange_count = Math.rand(@age..AGE_TO_DIE) * Math.log(@age) * ORANGE_COUNT_RELATIVE_TO_AGE
end
def pick_an_orange
if (@age == AGE_TO_DIE)
puts "Sorry, the Orange tree is dead"
elsif (@orange_count > 0)
@orange_count -= 1
puts "The Orange is delicious"
else
puts "Sorry, no Oranges to pick"
end
end
end
class Worker
def initialize(mutex, cv, orange_tree)
@mutex = mutex
@cv = cv
@orange_tree = orange_tree
end
def do_some_work
Thread.new do
until (@orange_tree.age == OrangeTree.AGE_TO_DIE)
@mutex.synchronize do
sleep_time = rand(0..5)
puts "Orange picker going to sleep for #{sleep_time}"
sleep(sleep_time)
puts "Orange picker woke up after sleeping for #{sleep_time}"
@orange_tree.pick_an_orange
puts "Orange picker waiting patiently..."
@cv.wait(@mutex)
end
end
end
Thread.new do
until (@orange_tree.age == OrangeTree.AGE_TO_DIE)
@mutex.synchronize do
sleep_time = rand(0..5)
puts "Age increaser going to sleep for #{sleep_time}"
sleep(sleep_time)
puts "Age increaser woke up after sleeping for #{sleep_time}"
@orange_tree.one_year_passes
puts "Age increaser increased the age"
@cv.signal
end
end
end
end
Worker.new(Mutex.new, ConditionVariable.new, OrangeTree.new).do_some_work
until (@orange_tree.age == OrangeTree.AGE_TO_DIE)
# wait for the Threads to finish
end
end
@orange_tree
是Worker對象的實例變量,只能從對象內部訪問。 您嘗試在“直到”條件(不存在)下從全局范圍訪問它。 有幾種解決方法,但是這需要最少的更改:
...
orange_tree = OrangeTree.new
Worker.new(Mutex.new, ConditionVariable.new, orange_tree).do_some_work
until (orange_tree.age == OrangeTree::AGE_TO_DIE)
...
您還應該研究Thread#join
: http : //www.ruby-doc.org/core-1.9.3/Thread.html#method-i-join 。 它會照顧您的等待。 其余的多線程代碼在技術上看起來都是正確的。 我確定您知道,如果這不僅僅是一項練習,那么您將希望使互斥鎖更加精細。 就像現在那樣,這兩個線程將幾乎互斥地執行,這會破壞線程的作用。
另外,查找attr_accessor
或attr_reader
。 它們將節省您手動定義OrangeTree#height
, age
等的OrangeTree#height
。
多聯接示例
threads = []
threads << Thread.new do
...
end
threads << Threads.new do
...
end
threads.each { |thread| thread.join }
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