Monthly Archives: April 2011

The future of web startups

Posted on by

So you end up with a world in which high school students think they need to get good grades to get into elite colleges, and college students think they need to get good grades to impress employers, within which the employees waste most of their time in political battles, and from which consumers have to buy anyway because there are so few choices.

Imagine if that sequence became a big, straight pipe. Then the effects of being measured by performance would propagate all the way back to high school, flushing out all the arbitrary stuff people are measured by now. That is the future of web startups.

— Paul Graham

2011.04.29 Friday ACHK

塗改風暴 3.1

Posted on by

這段改編自 2010 年 5 月 1 日的對話。

考試的其中一個重要技巧是，不要用塗改液。

（CSK：我剛剛才買了一支塗改帶。）

毋須使用。如果寫了錯東西，就用手上的筆把它劃掉便行。如果要劃掉一大段東西，我建議使用鉛筆，因為，萬一之後發現劃錯了的話，你可以「還原」。

— Me@2011.04.28

2011.04.28 Thursday (c) All rights reserved by ACHK

MapReduce 2

Posted on by

MapReduce is a framework for processing huge datasets on certain kinds of distributable problems using a large number of computers (nodes), collectively referred to as a cluster (if all nodes use the same hardware) or as a grid (if the nodes use different hardware). Computational processing can occur on data stored either in a filesystem (unstructured) or within a database (structured).

“Map” step: The master node takes the input, partitions it up into smaller sub-problems, and distributes those to worker nodes. A worker node may do this again in turn, leading to a multi-level tree structure. The worker node processes that smaller problem, and passes the answer back to its master node.

“Reduce” step: The master node then takes the answers to all the sub-problems and combines them in some way to get the output — the answer to the problem it was originally trying to solve.

— Wikipedia on MapReduce

2011.04.27 Wednesday ACHK

A time to fear

Posted on by

Time Theory of Fear

Do the thing you fear, the fear disappears.

If you do not do something your fear, that thing remains in your future.

Future implies possibilities and uncertainties. The fear is due to the uncertainties.

But once you have started the thing your fear, the thing is already in your present.

The uncertainty is much less.

The fear before an exam is greater than the fear during the exam.

The fear before an announcement of exam results is greater than the fear after.

– Me@2009.11.07

2011.04.26 Tuesday (c) All rights reserved by ACHK

免責條款

Posted on by

我的網誌，紀錄了我平日傳授給學生的讀書方法。而那些技巧，是根據我個人的讀書和教學經驗，改編加工而成的。一開始介紹它們給新的學生時，我通常都會作一些「免責聲明」。

我的讀書方法，只是供大家參考。如果你本身有讀書方法，而又行之有效的話，根本沒有必要理會。相反，如果你本身成績不理想，而又對讀書方法毫無頭緒的話，你可以暫時嘗試使用我的提議。長遠來說，你應該以我的讀書方法作為起點，然後把它們逐步修改，直到改編成最適合你自己的版本為止。

— Me@2011.04.26

2011.04.26 Tuesday (c) All rights reserved by ACHK

大智若愚

Posted on by

這段改篇自 2010 年 5 月 1 日的對話。

題目問你什麼，你就答什麼，不要答多，不要答少。千萬不要為了表演自己的數學知識，而添加額外的解釋，因為閱卷員不會有時間理會它們。

…

（CKY：除了你的方法以外，我還想到這個方法。）

我的方法比你的方法好。你的方法要聰明的人才可以掌握；而我的方法任何人都可以掌握。你的方法要精神狀態好時才想得出來；而我的方法任何時候也可以想得出來，因為我的方法十分「愚蠢」，根本連想到不用想，就自然記得。

記住，考試時的唯一目標，是奪取最多的分數，而不是炫耀自己的智力。

— Me@2011.04.24

2011.04.24 Sunday (c) All rights reserved by ACHK

Broken symmetry 2

Posted on by

diff 3b

.

Mostly it is loss which teaches us about the worth of things.

— Arthur Schopenhauer

.

Anything that does not change you cannot see, because it falls into the background.

你不會到留意「正常」的事物，因為，它們會化成「背景」。

— Me@2011.04.22

.

想知一件事物的價值，你先要嘗試失去它。

你不會到留意「正常」的事物，因為腦部毋須處理「正常」的事物，所以會自動忽略它們，以節省資源去解決「問題」。（「問題」就是不如意的事物。）

— Me@2011.04.24

.

.

2011.04.24 Sunday (c) All rights reserved by ACHK

一點點精采 2

Posted on by

網誌時代 10

我發覺我和學生的對話中，來來去去都是回答同一堆的問題，例如：

「我快要考試，但來不及溫習。我應該怎麼辦呢？」

「我溫習了的東西，幾日之後就忘記了。」

「我那天用了兩個小時，研究一題數學題目，結果其他東西沒有足夠時間去完成。」

「昨天是假期，我原本打算早上九時起來溫習。但是，我睡到十一時才醒，斷送了兩個小時，令我內疚非常。結果，我花了整天的時間去內疚，不能專心溫習。」

人所遇到的問題，有一部分是共通的，而又不斷重複。

— Me@2011.04.23

2011.04.23 Saturday (c) All rights reserved by ACHK

MapReduce

Posted on by

By abstracting away the very concept of looping, you can implement looping any way you want, including implementing it in a way that scales nicely with extra hardware.

Without understanding functional programming, you can’t invent MapReduce, the algorithm that makes Google so massively scalable. The terms Map and Reduce come from Lisp and functional programming. MapReduce is, in retrospect, obvious to anyone who remembers from their 6.001-equivalent programming class that purely functional programs have no side effects and are thus trivially parallelizable.

The very fact that Google invented MapReduce, and Microsoft didn’t, says something about why Microsoft is still playing catch up trying to get basic search features to work, while Google has moved on to the next problem: building Skynet^H^H^H^H^H^H the world’s largest massively parallel supercomputer. I don’t think Microsoft completely understands just how far behind they are on that wave.

— Can Your Programming Language Do This?

— Joel Spolsky

2011.04.22 Friday ACHK

心理狀態管理

Posted on by

一步 1.2

這段改篇自 2010 年 5 月 1 日的對話。

所以，你做任何一部分時，應該用紙遮蓋著之後的部分，讓自己看不到它們，直到你完成眼前的部分為止。那樣，一方面，你不會被之後的部分所分心。另一方面，你的心理負擔會輕盈了一些。

試想想，當你正在做 a 部分，萬一不慎看到 b 部分，而又發覺不是立刻懂做的話，你的心裡就會產生不必要的不安，從而減低你做到 a 部分的機會。

（CKY：這個技巧，好像是在催眠著自己。）

不要輕視這些小動作的重要性。考試有很大部分，是在鬥心理狀態管理。心理狀態管理得好，勝算會大很多。

— Me@2011.04.21

2011.04.21 Thursday (c) All rights reserved by ACHK

Gauge theory 5

Posted on by

The importance of gauge theories for physics stems from the tremendous success of the mathematical formalism in providing a unified framework to describe the quantum field theories of electromagnetism, the weak force and the strong force. This theory, known as the Standard Model, accurately describes experimental predictions regarding three of the four fundamental forces of nature, and is a gauge theory with the gauge group SU(3) × SU(2) × U(1). Modern theories like string theory, as well as some formulations of general relativity, are, in one way or another, gauge theories.
 
— Wikipedia on Gauge theory

2011.04.18 Monday ACHK

不敵天氣 2

Posted on by

You can spend your whole life trying to be popular, but at the end of the day, the size of the crowd at your funeral will be largely dictated by the weather.

— Frank Skinner

你可以花一生的時間，令到自己受歡迎；但是，你的喪禮將會有多少人出席，還要視乎當日的天氣。

— Me@2010.07.16

2011.04.18 Monday (c) All rights reserved by ACHK

一點點精采 1.3

Posted on by

網誌時代 9.3

（安：回想以前，我們的對話內容之中，其實有很多也值得化成文字。幾年前的對話，我們沒有錄音，沒有紀錄下來，真的有一點點可惜。）

可惜的程度不大。重點是，你我還健在。真正重要的內容，在往後的對話中，自然會重新出現。不會重新出現的，即是無關痛癢。

— Me@2011.04.17

2011.04.17 Sunday (c) All rights reserved by ACHK

Soliton

Posted on by

In mathematics and physics, a soliton is a self-reinforcing solitary wave (a wave packet or pulse) that maintains its shape while it travels at constant speed. Solitons are caused by a cancellation of nonlinear and dispersive effects in the medium.

Dispersion and non-linearity can interact to produce permanent and localized wave forms. Consider a pulse of light traveling in glass. This pulse can be thought of as consisting of light of several different frequencies. Since glass shows dispersion, these different frequencies will travel at different speeds and the shape of the pulse will therefore change over time. However, there is also the non-linear Kerr effect: the refractive index of a material at a given frequency depends on the light’s amplitude or strength. If the pulse has just the right shape, the Kerr effect will exactly cancel the dispersion effect, and the pulse’s shape won’t change over time: a soliton.

— Wikipedia on Soliton

2011.04.17 Sunday ACHK

Operating system 3

Posted on by

No one cares what operating system you run as long as it stays up.

— Bruce Perens

That’s why the best choice of software is often no software — and barring that, as little software as you can possibly get away with, and even then, only from the most reputable and reliable sources.

— Coding Horror

— by Jeff Atwood

The greatest of rulers hardly dwells upon the minds of his subjects,
Lesser than this they forever draw near and laud him with great praise,
Lesser than this the people are held in his frightening awe and fear,
Lesser than this the people revile and curse him.
   
太上，下知有之；
其次，親而譽之；
其次畏之；
其次侮之。

— Laozi (Wikisource translation)

2011.04.16 Saturday ACHK