在一个特殊的场景中，c++仍然占据上风(并且将在未来几年占据上风)，即可以在编译时预先确定多态决策。

通常，封装和延迟决策是一件好事，因为它使代码更加动态，更容易适应不断变化的需求，并且更容易作为框架使用。这就是为什么在c#中面向对象编程是非常高效的，并且它可以在术语“泛化”下泛化。不幸的是，这种特殊的泛化在运行时是有代价的。

Usually, this cost is non-substantial but there are applications where the overhead of virtual method calls and object creation can make a difference (especially since virtual methods prevent other optimizations such as method call inlining). This is where C++ has a huge advantage because you can use templates to achieve a different kind of generalization which has no impact on runtime but isn't necessarily any less polymorphic than OOP. In fact, all of the mechanisms that constitute OOP can be modelled using only template techniques and compile-time resolution.

在这种情况下(不可否认，它们通常局限于特殊的问题领域)，c++胜过c#和类似的语言。

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.

c#和c++在性能方面有一些主要的区别:

c#是基于GC /堆的。分配和GC本身是内存访问的非局部性开销 多年来，c++优化器已经变得非常好。JIT编译器无法达到相同的级别，因为它们只有有限的编译时间，并且看不到全局作用域

除此之外，程序员的能力也很重要。我见过一些糟糕的c++代码，其中的类通过值作为参数传递。在c++中，如果你不知道自己在做什么，实际上会让性能变差。

没有严格的理由说明为什么基于字节码的语言(如c#或Java)不能像c++代码一样快。然而，c++代码在很长一段时间内都要快得多，今天在许多情况下仍然如此。这主要是因为更高级的JIT优化实现起来比较复杂，而真正酷的JIT优化现在才出现。

所以在很多情况下，c++更快。但这只是答案的一部分。c++实际上更快的情况是高度优化的程序，其中专业程序员彻底优化了代码。这不仅非常耗时(因此非常昂贵)，而且由于过度优化通常会导致错误。

On the other hand, code in interpreted languages gets faster in later versions of the runtime (.NET CLR or Java VM), without you doing anything. And there are a lot of useful optimizations JIT compilers can do that are simply impossible in languages with pointers. Also, some argue that garbage collection should generally be as fast or faster as manual memory management, and in many cases it is. You can generally implement and achieve all of this in C++ or C, but it's going to be much more complicated and error prone.

As Donald Knuth said, "premature optimization is the root of all evil". If you really know for sure that your application will mostly consist of very performance critical arithmetic, and that it will be the bottleneck, and it's certainly going to be faster in C++, and you're sure that C++ won't conflict with your other requirements, go for C++. In any other case, concentrate on first implementing your application correctly in whatever language suits you best, then find performance bottlenecks if it runs too slow, and then think about how to optimize the code. In the worst case, you might need to call out to C code through a foreign function interface, so you'll still have the ability to write critical parts in lower level language.

请记住，优化一个正确的程序相对容易，但更正一个优化的程序要难得多。

给出实际的速度优势百分比是不可能的，这在很大程度上取决于你的代码。在许多情况下，编程语言实现甚至不是瓶颈。请带着极大的怀疑态度使用http://benchmarksgame.alioth.debian.org/上的基准测试，因为这些测试的主要是算术代码，很可能与您的代码完全不同。

如果我没记错的话，c#模板是在运行时确定的。这肯定比c++的编译时模板慢。

当你考虑到很多人提到的所有其他编译时优化，以及安全性的缺失，确实意味着更高的速度……

我想说，就原始速度和最小内存消耗而言，c++是显而易见的选择。但这也转化为更多的时间来开发代码，并确保您不会泄漏内存或导致任何空指针异常。

结论:

c#:更快的开发，更慢的运行 c++:开发慢，运行快。

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。