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  Surprising applications of math

The comments in the previous post touched on surprising applications of math, so I thought I’d expand this theme into it’s own post. Below I’ll give a couple general examples of surprising applications and then I’ll give a couple more personal applications I found surprising.Number theory has traditionally been the purest of pure mathematics. People study number theory for the joy of doing so, not to make money. At least that was largely true until the ...

   Math,Number theory,Algorithms,Differential euqation     2011-11-18 09:24:19

  "Simplicity" is not a simple concept

I've come to avoid using the word "Simplicity" or its variants ("Simple," &c.) It means too many different things to different people.For example, my original land-line phone was simple:It's simple by eliminating extraneous use cases. It only handles one user scenario, the one that was the most common when it was invented. If we think of the number of affordances and the number of uses, this kind of simplicity lowers the number of affordances by lowering the number of uses. I call this kind ...

   Simplicity,Software,Usability,iPhone,Phone     2011-11-24 09:21:09

  A Perl Regular Expression That Matches Prime Numbers

perl -lne '(1x$_) =~ /^1?$|^(11+?)\1+$/ || print "$_ is prime"' Can you figure out how it works? I give an explanation below, but try to figure it out yourself. Here is what happens when you run it: $ perl -lne '(1x$_) =~ /^1?$|^(11+?)\1+$/ || print "$_ is prime"' 1 2 2 is prime 3 3 is prime 4 5 5 is prime 6 7 7 is prime 8 9 10 11 11 is prime Here is how it works. First, the number is converted in its unary representation by (1x$_). For example, the number 5 gets converted into 1x5, which is ...

   Perl,Regex,Regular expression,Prime number,One line     2011-12-26 08:42:00

  Code Optimization Techniques for Graphics Processing Units

Books on parallel programming theory often talk about such weird beasts like the PRAM model, a hypothetical hardware that would provide the programmer with a number of processors that is proportional to the input size of the problem at hand. Modern general purpose computers afford only a few processing units; four is currently a reasonable number. This limitation makes the development of highly parallel applications quite difficult to the average computer user. However, the low cost and th...

   Optimazation,GUI,Graphic processing     2011-12-18 01:11:53

  Want to be a software engineer? Go to university

This editorial was originally submitted to the Sydney Morning Herald in response to an editorial proclaiming that people wanting to become software engineers should not attend university and instead learn a current popular programming language.   Over the past few years I’ve developed software for large corporations, started the Vodafail campaign, co-founded Mijura and represented Australia in the global Robocup (humanoid robotic soccer) competition. I graduated from University...

   Software engineer,University,Systematic study,Research     2011-12-07 08:48:54

  Some laws of interactive design

The well known quote from Alan Cooper is   Conforming to the standard unless there is a better choice. There are some best practices in interaction design. How many do you know? 1. Fitts' Law The time from one start point to target point is determined by two parameters: The distance to the target and the size of the target. )D and W in above picture), the formula is : T=a+blog2(D/W+1). It was first proposed by Paul Fitts, it is mathematical model used to predict the time from any poin...

   interaction design, laws, Fitts' law     2012-11-16 11:25:24

  The significance of coding competition to actual work

Some friends asked this question: In secondary schools we participate in the NOI, in university we participate in ACM/ICPC, TopCoder.What's the significance of coding competition to actual work? I participated in the NOI from 1994 to 1996, ACM/ICPC from 1999 to 2000 and TopCoder in 2002 for six months. Later I paid little attention to coding competition, so I may not understand the changes in recent years and race mode . The capabilities we can get by participating the competition can be summari...

   ACM,Programming,Facebook,TopCoder     2013-02-28 20:38:23

  Practice of using spinlock instead of mutex

Spinlock and mutex are two important concepts in multithreading programs. They are used to lock some shared resource to prevent concurrent access which may affect data consistency. But they do have differences, what are the differences? when should we use spinlock instead of mutex? The Theory In theory, when a thread tries to lock a mutex and it does not succeed, because the mutex is already locked, it will go to sleep, immediately allowing another thread to run. It will continue to sleep until...

   Spinlock,Mutex,Concurrency     2014-04-19 21:54:12

  One reason why mcrypt responds slowly

This morning one colleague came over and talked about one script which used mcrypt responded very slowly, the server configurations are fine. But the reason for the slowness is unknown. Here is one script which reproduces the issue: <?php $dmcryptText = "dummy"; $key = "foobar"; $size = mcrypt_get_iv_size(MCRYPT_BLOWFISH,MCRYPT_MODE_ECB); $iv = mcrypt_create_iv($size); //Take care $m = mcrypt_ecb(MCRYPT_BLOWFISH, $key, $dmcryptText, MCRYPT_DECRYPT, $iv); var_dump($m); When 20 requests of&...

   SOLUTION,SLOW,MCRYPT,RESPONSE,PHP     2012-09-27 12:03:16

  Android Hardware Buttons are not broken, let me tell you why

This post is written as a reaction on Christoffer Du Rietz’s article The Android Hardware-Buttons Are Broken. In his article Christoffer explains how the Android back button shows inconsistent behavior like doing different actions when it is used on the same screen.In the following article I will try to explain that this behavior is not broken. Instead it is exactly what the Android developers had in mind while designing the back button behavior.The way the back button is broken according...

   Android,Hardware,Button,Protect     2011-11-03 13:38:21

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