在听StackOverflow播客的时候,经常有人说“真正的程序员”是用C语言编写的,而C语言的速度要快得多,因为它“接近机器”。把前面的断言留到另一篇文章,C有什么特别之处,使它比其他语言更快?或者换句话说:什么能阻止其他语言编译成二进制代码,使其运行速度与C语言一样快?


当前回答

这实际上是一个长期存在的谎言。虽然C程序确实经常更快,但情况并非总是如此,特别是当C程序员不太擅长它的时候。

人们往往会忘记的一个明显的漏洞是,当程序必须为某种IO阻塞时,比如任何GUI程序中的用户输入。在这些情况下,使用什么语言并不重要,因为您受到数据传入速度的限制,而不是处理数据的速度。在这种情况下,不管你使用的是C、Java、c#甚至Perl;你不能比数据进入的速度更快。

The other major thing is that using garbage collection and not using proper pointers allows the virtual machine to make a number of optimizations not available in other languages. For instance, the JVM is capable of moving objects around on the heap to defragment it. This makes future allocations much faster since the next index can simply be used rather than looking it up in a table. Modern JVMs also don't have to actually deallocate memory; instead, they just move the live objects around when they GC and the spent memory from the dead objects is recovered essentially for free.

This also brings up an interesting point about C and even more so in C++. There is something of a design philosophy of "If you don't need it, you don't pay for it." The problem is that if you do want it, you end up paying through the nose for it. For instance, the vtable implementation in Java tends to be a lot better than C++ implementations, so virtual function calls are a lot faster. On the other hand, you have no choice but to use virtual functions in Java and they still cost something, but in programs that use a lot of virtual functions, the reduced cost adds up.

其他回答

这实际上是一个长期存在的谎言。虽然C程序确实经常更快,但情况并非总是如此,特别是当C程序员不太擅长它的时候。

人们往往会忘记的一个明显的漏洞是,当程序必须为某种IO阻塞时,比如任何GUI程序中的用户输入。在这些情况下,使用什么语言并不重要,因为您受到数据传入速度的限制,而不是处理数据的速度。在这种情况下,不管你使用的是C、Java、c#甚至Perl;你不能比数据进入的速度更快。

The other major thing is that using garbage collection and not using proper pointers allows the virtual machine to make a number of optimizations not available in other languages. For instance, the JVM is capable of moving objects around on the heap to defragment it. This makes future allocations much faster since the next index can simply be used rather than looking it up in a table. Modern JVMs also don't have to actually deallocate memory; instead, they just move the live objects around when they GC and the spent memory from the dead objects is recovered essentially for free.

This also brings up an interesting point about C and even more so in C++. There is something of a design philosophy of "If you don't need it, you don't pay for it." The problem is that if you do want it, you end up paying through the nose for it. For instance, the vtable implementation in Java tends to be a lot better than C++ implementations, so virtual function calls are a lot faster. On the other hand, you have no choice but to use virtual functions in Java and they still cost something, but in programs that use a lot of virtual functions, the reduced cost adds up.

使用现代优化编译器,纯C程序不太可能比编译后的。net代码快得多,如果有的话。通过像。net这样的框架为开发人员提供的生产力提高,您可以在一天内完成过去用普通c语言需要几周或几个月才能完成的工作。再加上与开发人员的工资相比,硬件成本低廉,用高级语言编写这些东西并以任何缓慢的速度抛出硬件要便宜得多。

The reason Jeff and Joel talk about C being the "real programmer" language is because there is no hand-holding in C. You must allocate your own memory, deallocate that memory, do your own bounds-checking, etc. There's no such thing as new object(); There's no garbage collection, classes, OOP, entity frameworks, LINQ, properties, attributes, fields, or anything like that. You have to know things like pointer arithmetic and how to dereference a pointer. And, for that matter, know and understand what a pointer is. You have to know what a stack frame is and what the instruction pointer is. You have to know the memory model of the CPU architecture you're working on. There is a lot of implicit understanding of the architecture of a microcomputer (usually the microcomputer you're working on) when programming in C that simply is not present nor necessary when programming in something like C# or Java. All of that information has been off-loaded to the compiler (or VM) programmer.

C语言速度很快,因为它是原生编译的低级语言。但是C不是最快的。递归斐波那契基准测试表明Rust、Crystal和Nim可以更快。

里面有很多问题——大部分是我没有资格回答的问题。但对于最后一个:

有什么能阻止其他语言编译成运行速度和C一样快的二进制呢?

一句话,抽象。

C语言只比机器语言高出一到两个抽象层次。Java和. net语言距离汇编程序至少有3个抽象级别。Python和Ruby我不太确定。

通常,程序员的玩具越多(复杂的数据类型等),你离机器语言的距离就越远,需要做的翻译就越多。

我在这里和那里都偏离了,但这是基本的要点。

更新-------这篇文章有一些很好的评论,有更多的细节。

我猜你忘了汇编语言也是一种语言:)

但是说真的,只有当程序员知道自己在做什么的时候,C程序才会更快。你可以很容易地编写一个C程序,它比用其他语言编写的程序运行得更慢。

C语言之所以更快,是因为它就是这样设计的。它允许你做很多“低级”的事情,帮助编译器优化代码。或者,我们可以说,你程序员负责优化代码。但这通常相当棘手,而且容易出错。

其他语言,就像前面提到的其他语言一样,更关注程序员的生产力。人们普遍认为程序员的时间比机器的时间要昂贵得多(即使在过去)。因此,尽量减少程序员花在编写和调试程序上的时间,而不是减少程序的运行时间,是很有意义的。为了做到这一点,您将牺牲一些可以使程序更快的事情,因为许多事情都是自动化的。