真正的不安全code性能 [英] True Unsafe Code Performance

问题描述

我明白不安全code是比较合适的访问之类的东西在Windows API并做不安全型铸件比写更高性能code，但我想问问你，如果你有没有注意到任何显著的性能通过使用其实际应用中的改进相比，安全的C＃code。

解决方案

有些性能测量

性能优势并不像你想象的那么大。

我做的正常管理数组访问与不安全的指针一些性能测试在C＃。

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从Visual Studio 2010的外运行构建，.NET 4，使用结果
任何CPU |在下列PC规格发布版本：的基于x64的PC，1四核处理器。 Intel64位家族6型号23步进10 GenuineIntel〜2833兆赫的

 线性阵列的访问权限
 00：00：07.1053664的普通
 00：00：07.1197401不安全*（P + I）线性阵列的访问 - 与指针递增
 00：00：07.1174493的普通
 00：00：10.0015947不安全（* P ++）随机数组访问
 00：00：42.5559436的普通
 00：00：40.5632554不安全使用的Parallel.For（），有4个处理器的随机数组访问
 00：00：10.6896303的普通
 00：00：10.1858376不安全
 

注意不安全 *（P ++）成语居然跑慢。我想这打破了被合并的循环变量，并在安全的版本（编译器生成）的指针访问，编译器优化。

来源$ C ​​$ C在 github上。

I understand unsafe code is more appropriate to access things like the Windows API and do unsafe type castings than to write more performant code, but I would like to ask you if you have ever noticed any significant performance improvement in real-world applications by using it when compared to safe c# code.

解决方案

Some Performance Measurements

The performance benefits are not as great as you might think.

I did some performance measurements of normal managed array access versus unsafe pointers in C#.

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Results from a build run outside of Visual Studio 2010, .NET 4, using an Any CPU | Release build on the following PC specification: x64-based PC, 1 quad-core processor. Intel64 Family 6 Model 23 Stepping 10 GenuineIntel ~2833 Mhz.

Linear array access
 00:00:07.1053664 for Normal
 00:00:07.1197401 for Unsafe *(p + i)

Linear array access - with pointer increment
 00:00:07.1174493 for Normal
 00:00:10.0015947 for Unsafe (*p++)

Random array access
 00:00:42.5559436 for Normal
 00:00:40.5632554 for Unsafe

Random array access using Parallel.For(), with 4 processors
 00:00:10.6896303 for Normal
 00:00:10.1858376 for Unsafe

Note that the unsafe *(p++) idiom actually ran slower. My guess this broke a compiler optimization that was combining the loop variable and the (compiler generated) pointer access in the safe version.

Source code available on github.

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