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
我认为没有人提到这样一个事实,即在C编译器上投入的精力比任何其他编译器都要多,也许Java是例外。
由于前面提到的许多原因,C是非常可优化的——几乎比任何其他语言都要多。因此,如果在其他语言编译器上投入同样的精力,C可能仍然会名列前茅。
I think there is at least one candidate language that with effort could be optimized better than C and thus we could see implementations that produce faster binaries. I'm thinking of digital mars D because the creator took care to build a language that could potentially be better optimized than C. There may be other languages that have this possibility. However I cannot imagine that any language will have compilers more than just a few percent faster than the best C compilers. I would love to be wrong.
我认为真正的“唾手可得的果实”将是那些被设计为易于人类优化的语言。一个熟练的程序员可以让任何语言运行得更快——但有时你不得不做一些荒谬的事情或使用不自然的结构来实现这一点。尽管这总是需要付出努力,但一种好的语言应该产生相对快速的代码,而不必纠结于程序究竟是如何编写的。
It's also important (at least to me) that the worst case code tends to be fast. There are numerous "proofs" on the web that Java is as fast or faster than C, but that is based on cherry picking examples. I'm not big fan of C, but I know that ANYTHING I write in C is going to run well. With Java it will "probably" run within 15% of the speed, usually within 25% but in some cases it can be far worse. Any cases where it's just as fast or within a couple of percent are usually due to most of the time being spent in the library code which is heavily optimized C anyway.
其他回答
与其说C的速度快,不如说C的成本模型是透明的。如果一个C程序慢,它的慢是通过一个明显的方式:执行很多语句。与C语言中操作的代价相比,对对象(特别是反射)或字符串的高级操作可能具有不明显的代价。
标准ML(使用MLton编译器)和Objective Caml这两种语言通常编译成二进制文件的速度与C语言一样快。如果你检查一下基准测试游戏,你会发现对于一些基准测试,比如二叉树,OCaml版本比c更快(我没有找到任何MLton的条目)。但不要把枪战看得太严重;正如它所说的,它是一个游戏,结果通常反映了人们在调优代码上投入了多少精力。
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。
c语言并没有什么特别之处,这也是它速度快的原因之一。
新语言支持垃圾收集、动态类型和其他功能,使程序员更容易编写程序。
问题在于,会有额外的处理开销,这会降低应用程序的性能。C语言没有这些,这意味着没有开销,但这意味着程序员需要能够分配内存并释放它们以防止内存泄漏,并且必须处理变量的静态类型。
也就是说,许多语言和平台,如Java(其Java虚拟机)和。net(其公共语言运行时),多年来通过即时编译(从字节码生成本机机器代码以实现更高性能)等技术改进了性能。
c++的平均速度更快(就像它最初一样,主要是C的超集,尽管有一些不同)。然而,对于特定的基准测试,通常有另一种更快的语言。
https://benchmarksgame-team.pages.debian.net/benchmarksgame/
fannjuch-redux是Scala中最快的
n-body和fasta在Ada中更快。
频谱范数在Fortran中是最快的。
反补、mandelbrot和pidigits在ATS中最快。
regex-dna是JavaScript中最快的。
chameneau -redux最快的是Java 7。
Haskell的螺纹环速度最快。
其余的基准测试在C或c++中是最快的。
C的设计者们已经做出了取舍。也就是说,他们决定把速度放在安全之上。C不会
检查数组下标边界 检查未初始化的变量值 检查内存泄漏 检查空指针解引用
当你索引到一个数组时,在Java中,它接受虚拟机中的一些方法调用,绑定检查和其他健全检查。这是有效的,绝对没问题,因为它在应有的地方增加了安全性。但是在C语言中,即使是非常微不足道的东西也不会被放在安全的地方。例如,C不要求memcpy检查要复制的区域是否重叠。它并不是一种用于编写大型商业应用程序的语言。
但是这些设计决策并不是C语言中的bug。它们是被设计出来的,因为它允许编译器和库编写者从计算机中获得每一点性能。下面是C语言的精神——C语言的基本原理文档是这样解释的:
C code can be non-portable. Although it strove to give programmers the opportunity to write truly portable programs, the Committee did not want to force programmers into writing portably, to preclude the use of C as a ``high-level assembler'': the ability to write machine-specific code is one of the strengths of C. Keep the spirit of C. The Committee kept as a major goal to preserve the traditional spirit of C. There are many facets of the spirit of C, but the essence is a community sentiment of the underlying principles upon which the C language is based. Some of the facets of the spirit of C can be summarized in phrases like Trust the programmer. Don't prevent the programmer from doing what needs to be done. Keep the language small and simple. Provide only one way to do an operation. Make it fast, even if it is not guaranteed to be portable. The last proverb needs a little explanation. The potential for efficient code generation is one of the most important strengths of C. To help ensure that no code explosion occurs for what appears to be a very simple operation, many operations are defined to be how the target machine's hardware does it rather than by a general abstract rule. An example of this willingness to live with what the machine does can be seen in the rules that govern the widening of char objects for use in expressions: whether the values of char objects widen to signed or unsigned quantities typically depends on which byte operation is more efficient on the target machine.