I suppose there are applications written in C# running fast, as well as there are more C++ written apps running fast (well C++ just older... and take UNIX too...) - the question indeed is - what is that thing, users and developers are complaining about ... Well, IMHO, in case of C# we have very comfort UI, very nice hierarchy of libraries, and whole interface system of CLI. In case of C++ we have templates, ATL, COM, MFC and whole shebang of alreadyc written and running code like OpenGL, DirectX and so on... Developers complains of indeterminably risen GC calls in case of C# (means program runs fast, and in one second - bang! it's stuck). To write code in C# very simple and fast (not to forget that also increase chance of errors. In case of C++, developers complains of memory leaks, - means crushes, calls between DLLs, as well as of "DLL hell" - problem with support and replacement libraries by newer ones... I think more skill you'll have in the programming language, the more quality (and speed) will characterize your software.

我想这么说:编写更快代码的程序员，是那些更了解当前机器运行速度的人，顺便说一句，他们也是那些使用适当工具的人，这些工具允许精确的低级和确定性优化技术。由于这些原因，这些人使用C/ c++而不是c#。我甚至认为这是事实。

We have had to determine if C# was comparable to C++ in performance and I wrote some test programs for that (using Visual Studio 2005 for both languages). It turned out that without garbage collection and only considering the language (not the framework) C# has basically the same performance as C++. Memory allocation is way faster in C# than in C++ and C# has a slight edge in determinism when data sizes are increased beyond cache line boundaries. However, all of this had eventually to be paid for and there is a huge cost in the form of non-deterministic performance hits for C# due to garbage collection.

需要大量内存访问的应用程序。图像处理通常更适合在非托管环境(c++)而不是托管环境(c#)中编写。使用指针算法优化的内循环在c++中更容易控制。在c#中，你可能需要使用不安全的代码来获得相同的性能。

对于“令人尴尬的并行”问题，当在c++上使用Intel TBB和OpenMP时，我观察到与用c#和TPL处理的类似(纯数学)问题相比，性能大约提高了10倍。SIMD是c#无法竞争的一个领域，但我也有一个印象，TPL有相当大的开销。

也就是说，我只在性能关键的任务中使用c++，我知道我将能够多线程并快速得到结果。对于其他任何事情，c#(偶尔f#)都很好。

快了5个橘子。或者更确切地说:不可能有一个(正确的)笼统的答案。c++是一种静态编译语言(但也有配置文件引导的优化)，c#在JIT编译器的帮助下运行。它们之间的差异如此之大，以至于像“快了多少”这样的问题都无法回答，甚至无法给出数量级。