十年学会编程

[337909] 主题：十年学会编程

	作者： redhat (RedHat)
	标题：十年学会编程
	来自： 192.168..
	发贴时间： 2005年04月10日 22:36:39
	长度： 16230字

	十年学会编程著者： Peter Norvig 翻译： Dai Yuwen ---------------------------------------------------------------- ------------- --- 为何人人都这么着急？信步走进任何一家书店，你会看到名为《如何在7天内学会Java》的书，还有各种各样的变体：在几天内或几小时内学会Visual Basic, Windows, Internet等等，等等。我在Am azon 上做了如下的强力检索： pubdate: after 1992 and title: days and (title: learn or title: teach yourself) 得到了248个结果。前78个都是计算机类书籍（第79个是 Learn Bengali in 30 days）。我用"hours"替换"days"，得到了类似的结果：更多的253书。前77本是计算机类书籍，第78本是 Teach Yourself Grammar and Style in 24 Hours。在前200 本书中，有96% 是计算机类书籍。结论是：要么人们都在急急忙忙地学习计算机，要么计算机比其它任何东西都容易学。没有书籍教你在几天内学会古典音乐、量子物理，或者是养狗，让我们分析一下，象一本名为《三天内学会Pascal》的书意味着什么：学习：在三天里，你没有时间写一些重大的程序，并从成功或失败中得益。你没有时间与有经验的程序员合作，并理解在那样的环境下工作是怎么回事。一句话，你不会有时间学到太多东西。因此他们只能谈论一些肤浅的东西，而不是深入的理解。正如亚力山大教皇所说，浅尝辄止是危险的事情。 Pascal：在三天时间里，你可能学会Pascal的语法（如果你已经学过类似的语言），但你学不到更多的如何使用这些语法的知识。也就是说，假如你曾是个BASI C程序员，你可以学着用Pascal语法写出BASIC风格的程序，但你不可能了解Pascal真正的好处（和坏处）。那么关键是什么？ Alan Perlis 说过：“一种不改变你编程的思维方式的语言，不值得去学。” 一种可能的情况是：你必须学一点儿Pascal（或可能性更大的象Visual Basic 或 JavaScript之类），因为你为了完成某种特定的任务，需要与一个现存的工具建立接口。不过那不是学习如何编程，而是在学习如何完成那个任务。三天内：很不幸，这不够，原因由下一节告诉我们。在十年里学会编程研究表明 (Hayes，Bloom)在任何一种领域内，象下棋、作曲、绘画、钢琴演奏、游泳、网球、以及原子物理学和拓扑学，等等，要达到专家水平大约都要化十年时间。没有真正的捷径：即使是莫扎特，4岁时就是音乐神童，13年后才开始写出世界级的作品。在另一方面，披头士似乎在1964年的Ed Sullivan表演上一炮走红。但他们从1 957年就开始表演，在获得大众青睐后，他们的第一个重大成功，Sgt. Peppers，是1967 年发行的。Sam uel Johnson 认为要花比十年更长的时间：“在任何领域中出类拔萃都要用毕生的劳作来取得；它不可能用较低的代价获得。” 而Chaucer感叹到：“人生短暂，学海无涯。 ” 这是我为编程成功开出的方子：设法对编程感兴趣，并且因为它有趣而编一些程序。确保编程一直充满足够乐趣，这样你才愿意投入十年宝贵时间。与其他程序员交流；阅读其它程序。这比任何书本或训练课程都重要。写程序。最好的学习方式是从实践中学习。用更技术性的话说，“在一个给定的领域内，个人的最大能力不是自动地由扩展了的经验取得的，但即使是高度有经验的人也可以通过有意识的努力来提高自己的能力” (p. 366) 和 “最有效的学习需要因人而异的适当难度，目标明确的任务，丰富的信息反馈，以及重复的机会和错误修正。” (p. 20-21) 此书 Cognition in Practice: Mind，Mathematics，and Cultur e in Everyday Life 是阐明此观点的令人感兴趣的参考文献。如果愿意，在大学里呆上4年或更长（在研究生院里）。你会接触到一些需要学历证明的工作，你会对此领域有更深的理解。如果你不喜欢学校，你可以（通过一些贡献）在工作中获得相似的经验。在任何情况下，光啃书本是不够的。Eric Raymond ，The New Hacker's Dictionary一书的作者，说过，“计算机科学不能把任何人变成编程专家，就象光研究刷子和颜料不会使人变成画家一样。” 我雇佣过的最好的程序员之一仅有高中程度；他做出了许多优秀的软件，有他自己的新闻组，而且通过股票期权，他无疑比我富有的多。和其他程序员一起做项目。在其中的一些项目中作为最好的程序员；而在另一些项目中是最差的。当你是最好的，你能测试领导项目的能力，用你的观点激发别人。当你是最差的，你学习杰出者是怎么做的，了解他们不喜欢做什么（因为他们吩咐你做事）。在其他程序员之后接手项目。使自己理解别人写的程序。当程序的原作者不在的时候，研究什么需要理解并且修改它。思考如何设计你的程序以便后来者的维护。学习至少半打的编程语言。包括一种支持类抽象的语言（象Java 或C++），一种支持函数化抽象的语言（象Lisp或ML），一种支持语法抽象的语言（象 Lisp），一种支持声明规格说明的语言（象Prolog或C++ 的模板），一种支持 coroutine的语言（象Icon或Sch eme），一种支持并行的语言（象Sisal）。请记住“计算机科学”中有“计算机”一词。了解你的计算机要花多长时间执行一条指令，从内存中取一个字（有cache），从磁盘中读取连续的字，和在磁盘中找到新的位置。（答案）使自己卷入一种语言标准化的工作里。它可以是ANSI C++委员会，也可以是决定你周围小范围内的编程风格是应该两个还是四个空格缩进。通过任何一种方式，你了解到其他人在某种语言中的想法，他们的理解深度，甚至一些他们这样想的原因。找到适当的理由尽快地从语言标准化的努力中脱身。明白了这些，仅从书本中你能得到多少就成了一个问题。在我第一个孩子出生前，我读了所有的（关于育儿的）How to 书籍，仍然感觉是个手足无措的新手。3 0个月以后，我的第二个孩子快要出生了，我回头温习这些书了吗？没有。相反，我依靠我的个人经验，它比专家写的数千页书更有用和可靠。 Fred Brooks在他的随笔《没有银弹》中定出了一个寻找优秀软件设计者的三步计划：尽可能早地，有系统地识别顶级的设计人员。为设计人员指派一位职业导师，负责他们技术方面的成长，仔细地为他们规划职业生涯。为成长中的设计人员提供相互交流和学习的机会。此计划假设某些人已经具备了杰出设计者的必要才能；要做的只是如何恰当地诱导他们。 Alan Perlis 说得更简明扼要：“每个人都能被教会雕刻：假如米开朗其罗被教成如何不会雕刻。同样的道理也适用于优秀的程序员。” 所以尽管买那本Java的书吧。你可能会从中学到点儿东西。但作为一个程序员，你不会在几天内或24小时内，哪怕是几个月内改变你的人生，或你实际的水平。参考文献 Bloom, Benjamin (ed.) Developing Talent in Young People, Ballant ine, 1985. Brooks, Fred, No Silver Bullets, IEEE Computer, vol. 20, no. 4, 1987, p. 10-19. Hayes, John R., Complete Problem Solver Lawrence Erlbaum, 1989. Lave, Jean, Cognition in Practice: Mind, Mathematics, and Cultur e in Everyday Life, Cambridge University Press, 1988. 答案 2001年夏天典型的1GHz PC的各种操作要花的时间执行一条指令 1 nsec = (1/1,000,000,000) sec 从L1 cache memory 中取一个字 2 nsec 从内存中取一个字 10 nsec 从磁盘的连续位置取一个字 200 nsec 从磁盘的新位置取一个字(seek) 8,000,000nsec = 8msec Peter Norvig (Copyright 2001) ---------------------------------------------------------------- ------------- --- Why is everyone in such a rush? Walk into any bookstore, and you'll see how to Teach Yourself Ja va in 7 Days alongside endless variations offering to teach Visual Basic, Windows, the Internet , and so on in a few days or hours. I did the following power search at Amazon.com: pubdate: after 1992 and title: days and (title: learn or title: teach yourself) and got back 248 hits. The first 78 were computer books (number 79 was Learn Bengali in 30 days). I replaced "days" with "hours" and got remarka bly similar results: 253 more books, with 77 computer books followed by Teach Yourself Grammar and Style in 24 Hours at numb er 78. Out of the top 200 total, 96% were computer books. The conclusion is that either people are in a big rush to learn about computers, or that computers are somehow fabulously easier to learn than anything else. There are no books on how to learn Beethoven, or Quantum Physics, or even Dog Grooming in a few days. Let's analyze what a title like Learn Pascal in Three Days could mean: Learn: In 3 days you won't have time to write several significan t programs, and learn from your successes and failures with them. You won't have time to work wi th an experienced programmer and understand what it is like to live in that environment. In short , you won't have time to learn much. So they can only be talking about a superficial familiarity, not a deep understanding. As Alexander Pope said, a little learning is a dangerous thing. Pascal: In 3 days you might be able to learn the syntax of Pasca l (if you already knew a similar language), but you couldn't learn much about how to use the synt ax. In short, if you were, say, a Basic programmer, you could learn to write programs in the style of Ba sic using Pascal syntax, but you couldn't learn what Pascal is actually good (and bad) for. So wh at's the point? Alan Perlis once said: "A language that doesn't affect the way you think about pro gramming, is not worth knowing". One possible point is that you have to learn a tiny bit of Pascal (o r more likely, something like Visual Basic or javascript) because you need to interface with an exist ing tool to accomplish a specific task. But then you're not learning how to program; you're learning to accomplish that task. in Three Days: Unfortunately, this is not enough, as the next se ction shows. Teach Yourself Programming in Ten Years Researchers (Hayes, Bloom) have shown it takes about ten years t o develop expertise in any of a wide variety of areas, including chess playing, music composition, pa inting, piano playing, swimming, tennis, and research in neuropsychology and topology. There appe ar to be no real shortcuts: even Mozart, who was a musical prodigy at age 4, took 13 more years b efore he began to produce world-class music. In another genre, the Beatles seemed to burst onto the sc ene, appearing on the Ed Sullivan show in 1964. But they had been playing since 1957, and while they ha d mass appeal early on, their first great critical success, Sgt. Peppers, was released in 1967. Samu el Johnson thought it took longer than ten years: "Excellence in any department can be attained on ly by the labor of a lifetime; it is not to be purchased at a lesser price." And Chaucer complained &qu ot;the lyf so short, the craft so long to lerne." Here's my recipe for programming success: Get interested in programming, and do some because it is fun. Ma ke sure that it keeps being enough fun so that you will be willing to put in ten years. Talk to other programmers; read other programs. This is more imp ortant than any book or training course. Program. The best kind of learning is learning by doing. To put it more technically, "the maximal level of performance for individuals in a given domain is not attained automatically as a function of extended experience, but the level of performance can be increas ed even by highly experienced individuals as a result of deliberate efforts to improve." (p. 366) and "the most effective learning requires a well-defined task with an appropriate difficulty leve l for the particular individual, informative feedback, and opportunities for repetition and corre ctions of errors." (p. 20-21) The book Cognition in Practice: Mind, Mathematics, and Culture in Everyda y Life is an interesting reference for this viewpoint. If you want, put in four years at a college (or more at a gradua te school). This will give you access to some jobs that require credentials, and it will give you a de eper understanding of the field, but if you don't enjoy school, you can (with some dedication) get simil ar experience on the job. In any case, book learning alone won't be enough. "Computer science educ ation cannot make anybody an expert programmer any more than studying brushes and pigment can make s omebody an expert painter" says Eric Raymond, author of The New Hacker's Dictionary. One of the best programmers I ever hired had only a High School degree; he's produced a lot of great software, has h is own news group, and through stock options is no doubt much richer than I'll ever be. Work on projects with other programmers. Be the best programmer on some projects; be the worst on some others. When you're the best, you get to test your abilities to lead a project, and to inspire others with your vision. When you're the worst, you learn what the mast ers do, and you learn what they don't like to do (because they make you do it for them). Work on projects after other programmers. Be involved in underst anding a program written by someone else. See what it takes to understand and fix it when the origin al programmers are not around. Think about how to design your programs to make it easier for those wh o will maintain it after you. Learn at least a half dozen programming languages. Include one l anguage that supports class abstractions (like Java or C++), one that supports functional ab straction (like Lisp or ML), one that supports syntactic abstraction (like Lisp), one that supports de clarative specifications (like Prolog or C++ templates), one that supports coroutines (like Icon or Sc heme), and one that supports parallelism (like Sisal). Remember that there is a "computer" in "computer science". Know how long it takes your computer to execute an instruction, fetch a word from memory (with and witho ut a cache miss), read consecutive words from disk, and seek to a new location on disk. (Answers he re.) Get involved in a language standardization effort. It could be t he ANSI C++ committee, or it could be deciding if your local coding style will have 2 or 4 space inden tation levels. Either way, you learn about what other people like in a language, how deeply they feel so, and perhaps even a little about why they feel so. Have the good sense to get off the language standardization effo rt as quickly as possible. With all that in mind, its questionable how far you can get just by book learning. Before my first child was born, I read all the How To books, and still felt like a clueless novice. 30 Months later, when my second child was due, did I go back to the books for a r efresher? No. Instead, I relied on my personal experience, which turned out to be far more useful and reassuring to me than the thousands of pages written by experts. Fred Brooks, in his essay No Silver Bullets identified a three-p art plan for finding great software designers: Systematically identify top designers as early as possible. Assign a career mentor to be responsible for the development of the prospect and carefully keep a career file. Provide opportunities for growing designers to interact and stim ulate each other. This assumes that some people already have the qualities necessa ry for being a great designer; the job is to properly coax them along. Alan Perlis put it more succinct ly: "Everyone can be taught to sculpt: Michelangelo would have had to be taught how not to. So it is wi th the great programmers". So go ahead and buy that Java book; you'll probably get some use out of it. But you won't change your life, or your real overall expertise as a programmer in 24 hours , days, or even months. References Bloom, Benjamin (ed.) Developing Talent in Young People, Ballant ine, 1985. Brooks, Fred, No Silver Bullets, IEEE Computer, vol. 20, no. 4, 1987, p. 10-19. Hayes, John R., Complete Problem Solver Lawrence Erlbaum, 1989. Lave, Jean, Cognition in Practice: Mind, Mathematics, and Cultur e in Everyday Life, Cambridge University Press, 1988. http://www.norvig.com/ Peter Norvig Google 2400 Bayshore Parkway Mountain View, CA 94043 Email: peter@norvig.com Phone: 650-623-4248 Fax: 650-618-1499 Web: norvig.com Note to recruiters: Please don't offer me a job. I already have the best job in the world at the best company in the world. Note to engineers, researchers, managers: see why you should app ly to help. Professional Employment (Full-Time) 2001-now Google Director of Search Quality 1998-2001 NASA Ames Research Center Division Chief, Computationa l Sciences 1996-1998 Junglee Corp. Chief Scientist 1994-1996 Harlequin, Inc. Chief Designer 1991-1994 Sun Microsystems Labs Senior Scientist 1986-1991 University of California, Berkeley Research Faculty Me mber 1985-1986 University of Southern California Assistant Professor 1978-1980 Higher Order Software, Inc. Member of Technical Staff 1977-1977 Woods Hole Oceanographic Institute Summer Programming Intern
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