Interlocked.CompareExchange<&诠释GT;使用GREATERTHAN或每种不超过，而不是平等

问题描述

的 System.Threading.Interlocked 对象允许加（减）和比较作为一个原子操作。看来，一个CompareExchange，只是没有做平等也GREATERTHAN /每种不超过作为一个原子比较是很有价值的。

The System.Threading.Interlocked object allows for Addition (subtraction) and comparison as an atomic operation. It seems that a CompareExchange that just doesn't do equality but also GreaterThan/LessThan as an atomic comparison would be quite valuable.

请问一个假设 Interlocked.GreaterThan 白细胞介素的特点还是一个CPU级别的功能？两者都是？

Would a hypothetical Interlocked.GreaterThan a feature of the IL or is it a CPU-level feature? Both?

由于缺乏任何其他选项，是有可能创造在C ++这样的功能或直接IL代码和公开该功能为C＃？

Lacking any other option, is it possible to create such a feature in C++ or direct IL code and expose that functionality to C#?

推荐答案

更新到后来的文章，我在这里提出：我们找到了一个更好的办法，使通过使用额外的锁对象的更大的比较。我们为了验证锁和互锁可以一起使用，但仅限于某些情况下，写了许多单元测试

Update to the later post I made here: we found a better way to make the greater comparison by using additional lock object. We wrote many unit tests in order to validate that a lock and Interlocked can be used together, but only for some cases.

如何代码工作：互锁使用内存壁垒一个读或写是原子。需要同步锁，使大于比较一个原子操作。所以规则是现在，这个类里面没有其他的操作将没有这个同步锁的价值。

How the code works: Interlocked uses memory barriers that a read or write is atomic. The sync-lock is needed to make the greater-than comparison an atomic operation. So the rule now is that inside this class no other operation writes the value without this sync lock.

我们得到这个类是可以很读取的互锁值速度快，但写操作多一点点。阅读是我们的应用程序要快2-4倍。

What we get with this class is an interlocked value which can be read very fast, but write takes a little bit more. Read is about 2-4 times faster in our application.

下面的代码视图：

看这里： http://files.thekieners.com/blogcontent/2012/ExchangeIfGreaterThan2.png

下面的代码复制并放;贴：密封

Here as code to copy&paste:

public sealed class InterlockedValue
{
    private long _myValue;
    private readonly object _syncObj = new object();

    public long ReadValue()
    {
        // reading of value (99.9% case in app) will not use lock-object, 
        // since this is too much overhead in our highly multithreaded app.
        return Interlocked.Read(ref _myValue);
    }

    public bool SetValueIfGreaterThan(long value)
    {
        // sync Exchange access to _myValue, since a secure greater-than comparisons is needed
        lock (_syncObj)
        {
            // greather than condition
            if (value > Interlocked.Read(ref  _myValue))
            {
                // now we can set value savely to _myValue.
                Interlocked.Exchange(ref _myValue, value);
                return true;
            }
            return false;
        }
    }
}

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