blocks|key|539403|text|你可能会得到很多答案，这就是我在尝试做一些“现实世界”应用程序时遇到的一个。我使用多线程和一些MVars来传递数据(MVar有点像锁定的共享内存)。我的典型模式是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|539404|a+<-+takeMVar+mvar
putMVar+mvar+(a+%2B+1)|code-block|syntax|javascript|539405|然后，只是有时候，当适当的条件发生时，我会这样做：|539406|a+<-+takeMVar+mvar
when+(a+>+10)+....|539407|问题是mvar的内容本质上是(0+%2B1%2B1%2B1%2B...)...which对于像100k这样的数字是相当密集的...这种类型的问题在我的代码中非常普遍；不幸的是，对于多线程应用程序，很容易遇到这样的问题。|539408|我所做的是在Detecting...what模式下启动haskell，该模式产生关于内存消耗的数据，启动和停止不同的线程，并查看内存占用是否稳定。|539409|Anotomy+of+a+thunk+leak+(with+instructions+how+to+debug+it)|offset|length|539410|一个例子：Thunk+memory+leak+as+a+result+of+map+function|539411|entityMap|0|LINK|mutability|MUTABLE|url|http://blog.ezyang.com/2011/05/anatomy-of-a-thunk-leak/|1|https://stackoverflow.com/questions/6630782/thunk-memory-leak-as-a-result-of-map-function^0|0|0|0|0|0|0|0|1N|0|0|5|19|1|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|16|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|18|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|19|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1A|8|@]|9|@$Q|1B|R|1C|1|1D]]|A|$]]|$1|S|3|T|5|6|7|1E|8|@]|9|@$Q|1F|R|1G|1|1H]]|A|$]]|$1|U|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|11]]|12|$5|X|Y|Z|A|$10|13]]]]

You will get probably many answeres, this is the one, I have encountered when trying to do some 'real-world' application.
I was using multithreading and some MVars to pass data around (MVar is something like locked shared memory). My typical pattern was:

<pre><code>a &lt;- takeMVar mvar
putMVar mvar (a + 1)
</code></pre>

And then, just sometimes, when a proper condition happened I did something like:

<pre><code>a &lt;- takeMVar mvar
when (a &gt; 10) ....
</code></pre>

The problem is that the content of mvar was essentially (0 + 1 + 1 + 1 + ....)...which was quite intensive for numbers like 100k... This type of problem was quite pervasive in my code; unfortunately for multithreading applications it's very easy to get into such problems.

Detecting...what I did was starting haskell in the mode that produces data regarding memory consumption, starting and stopping different threads and looking if memory footprint is stable or not...

<a href="http://blog.ezyang.com/2011/05/anatomy-of-a-thunk-leak/" rel="nofollow noreferrer">Anotomy of a thunk leak (with instructions how to debug it)</a>

An example: <a href="https://stackoverflow.com/questions/6630782/thunk-memory-leak-as-a-result-of-map-function">Thunk memory leak as a result of map function</a>

blocks|key|539471|text|在对大型数据结构进行递归时，我遇到了这个问题。堆积的数据块变得太多，然后就会出现空间泄漏。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|539472|在Haskell中，您需要经常意识到遇到空间泄漏的可能性。由于迭代不存在，基本上任何递归函数都有可能产生空间泄漏。|539473|要避免此问题，请记住递归函数，或以尾递归方式重写它们。|539474|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

I've run into this problem when doing recursion over large data structures. The built up thunks get to be too much and then you get a space leak. 

In Haskell, you need to be constantly aware of the possibility of running into a space leak. Since iteration doesn't exist, basically any recursive function has the potential to generate a space leak.

To avoid this problem, memoize recursive functions, or rewrite them tail-recursively.

I have read it many times that lazy evaluation in Haskell may sometimes lead to space leaks. What kind of code can lead to space leaks? How to detect them? And what precautions can be taken on part of a programmer to avoid them?

Space leaks in Haskell

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我已经读过很多次了，Haskell中的延迟计算有时可能会导致空间泄漏。哪种代码会导致空间泄漏？如何检测它们？程序员应该采取哪些预防措施来避免这种情况呢？

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