Vjeux

I'm working a lot with URLs that contain ids and very often, I made a mistake in one digit of the long id and end up with a completely different element. If I don't pay attention, then I end up looking at two elements thinking they are the same and am intrigued until I find out the mistake.

In order to avoid that, I wanted to know if I could make a sequence of ids where making one mistake would not give a valid id. For example, if you have the id 473, then you have to black list all the ids where the first digit is wrong (073, 173, 273, 373, 573, 673, 773, 873, 973) and the second being wrong (403, 413, 423, 433, 443, 453, 463, 483, 493) and the last one (470, 471, 472, 474, 475, 476, 477, 478, 479).

Here is the list of the first pseudo-numbers:

1. 011
2. 022
3. 033
4. 044
5. 055
6. 066
7. 077
8. 088
9. 099
10. 101
11. 110
12. 123
13. 132
14. 145
15. 154
16. 167
17. 176
18. 189
19. 198
20. 202
21. 213
22. 220
23. 231
24. 246
25. 257
26. 264
27. 275
28. 303
29. 312
30. 321
31. 330
32. 347
33. 356
34. 365
35. 374
36. 404
37. 415
38. 426
39. 437
40. 440
41. 451
42. 462
43. 473
44. 505
45. 514
46. 527
47. 536
48. 541
49. 550
50. 563
51. 572
52. 606
53. 617
54. 624
55. 635
56. 642
57. 653
58. 660
59. 671
60. 707
61. 716
62. 725
63. 734
64. 743
65. 752
66. 761
67. 770
68. 808
69. 819
70. 880
71. 891
72. 909
73. 918
74. 981
75. 990

And here is a visual representation of those numbers:

For each digit in the number, we blacklist 9 other numbers. For a 5 digits number (eg 12345), that means blacklisting 45 numbers. For a 10 digits number (eg 1234567890), that means blacklisting 90 numbers. The number of blacklisted numbers only grows at a logarithmic scale.

In order to see how many numbers we lose, I plotted the ratio of pseudo numbers count compared to the real numbers. We can roughly keep one number every fifteen. But the good news is that the ratio doesn't fall off the chart as the numbers grow.

Looking at the numbers, they looked like to go from 10 to 10 but with some huge spikes and sometimes they were closer. So I plotted the difference between two consecutive numbers in a chart and it looks like the difference is centered around 10. But the variance is getting higher and higher as you move further.

I'm not really sure if this sequence can be really useful in practice but that was a fun week-end experiment. I hope it'll give you some, hopefully useful, ideas 🙂

Lately, I've been advocating to all my student friends to start a blog. Here's an article with the most common questions answered 🙂

What are the benefits?

Being known as an expert. The majority of my blog posts are about advanced Javascript topics. As a result, I'm being tagged as the "Javascript" guy by people that know (broad sense) me. Every time they have a question about Javascript or Web Development they go to me.

Expanding your relations. Through my activities with this blog, I had conversations with celebs such as Bjarne Stroustrup (C++), Brendan Eich (Javascript), Jeremy Ashkenas (CoffeeScript) and many other people that I didn't know before. No one in my close relations is deeply interested in what I am writing. But thanks to the internet, I can meet other people that shares the same interests.

Getting Recruited. As you become an expert in a field, people start to notice and will want you. My blog is barely known and still, I have received several job offers. However this happens at random, take it like a gift but don't expect it to happen, or it won't 🙂

Being better. I've been so much better at Javascript since I started writing about it. But maintaining this blog also helped me improve my writing skills as well as my English.

Benefits are long term. You should not start a blog and expect it to be rewarding the next week. A blog is a presence on the internet. During the first 6 months, I barely had more than 5 visitors per day, but this number slowly started growing as I wrote more articles and time passed. Now, I'm at 100 visitors a day. I'm still amazed to see that so many people come!

Who cares about my blog?

Your friends. The first thing I do when I am done writing an article is to paste the link to some of my MSN contacts that will be vaguely interested in. It is a powerful way to start a conversation with people you did not talk with for a long time. I often re-write parts of the article given the feedback I receive and it leads to great conversations.

People on the Internet. My girlfriend always says "If you thought about it, someone did it". On the same idea, I believe that the following statement is correct: "If you find something interesting, someone else does too". Here is a fact, there are over 100 visitors on my blog everyday. Google connects people with the same interests!

People that want to know about you. The extreme example is your recruiter, but it could be a co-worker or even just a friend. Your blog is the place where you can show who you are and what you are worth. It is much better than a resume as it isn't constrained by a strong standardization and a ridiculous 1-page constraint.

I don't know what to write

Projects you've done. The easiest way to start a blog is to write one article per school/personal projects you have done. Put a screenshot, a description of what it does and you are set. This way, if I want to know about you, I will quickly scroll over your blog and will see what you have done. If something interests me, I'm going to read the article more closely.

Techniques you have used. It is interesting to go over your projects and allocate one blog article for each technical problem you solved. For example, the project Guild Recruitment leaded me to write several articles such as Dynamic Query Throttling, Mysqli Wrapper, Search Optimizations. The latest eventually made me look deeper to write Sorting Table.

Follow-up a conversation. I am often debating with my friends on topics related to computer science. Those discussions are potential targets for a blog post! It is really interesting to go deeper and start writing about it. You'll get more arguments to crush your friends theories 🙂

Start writing and ideas will flow. Once you have an article written, it often generates new ideas. Now, every time I write some code, I ask myself if that would be worth blogging. If yes, I create a draft on WordPress for later. This way when I'm in the mood of writing, I have many things to write.

There are already many article on the subject, why should I write mine?

Influence people around you. I always love reading my friends blog because they are talking about subjects that I'm interested in but that I would not have willingly researched for. It helps expanding my Javascript-centric horizon.

If you write about it, it means you know it. For example I wrote an article about how to use makedepend in makefiles. It tells recruiter multiple things. I have experienced the problem of dependency management. I am confortable with Makefiles as I used them in a fancy way. This is invaluable compared to a Makefile entry in a resume.

Go deeper in the subject. I often find myself writing code pretty easily without too much thinking. Writing about this particular sexy technique in my blog more challenging. It requires me to state the exact problem I try to solve, think about alternatives, seek for already existing solutions ...

After the post has been written, I receive a lot of feedback. My friends almost always talk about how it would have been solved in their own language of predilection. They also provide more use-cases where the technique would and wouldn't work, leads to improve it ...

How long does it take?

Count one evening per post. I usually spend one full evening writing down an involved article like this one. However I think a lot about the subject in a passive way by reading related articles, thinking about it in my bed ... Articles that show off a project are much quicker to write, I'd say about 30 minutes.

Post as often as you want. When I have something I deeply want to share I write an article about it. Once I've written once, I often see myself writing some more about drafts I had. Then there is a period of silence. Overall, I'd say I write every two months, often during holidays.

How many articles. Each new article you write is not going to shadow the other but adds up. When I check my analytics, each article written slightly increases my daily viewer count. But even with one article a blog is worth it.

How do I start?

Install a WordPress. Even if you are a geek, I strongly recommend against you coding your own blog or using some nerdy blog software. I went over that myself and I found myself coding stuff every time I wanted to write an article. WordPress gives you all the tools you need to blog, and if you want to do something a bit special, chances are there's already an extension that does it.

Quickly write your first article. Don't spend so much time finding the perfect theme or installing many extensions you don't even need yet. The first article is the hardest! Write it down and send it to your friends. Listen to their feedback and instead of editing the article, write another article trying to fix those issues. Writing is hard so it'll take more than one shot to feel comfortable with it. The more you practice, the easier it will be.

Conclusion

If I managed to convince your starting a blog, please give me the link! I'd love to read about your stuff and may help you get started if you want.

scladder.com

Popularity System

In Starcraft 2, the Custom Maps are being listed by popularity. The popularity is the number of times the map has been played for more than 5 minutes during the last 12 hours.

As I am running the website sc2mapster.com, I would like to have this listing. This would let the players know what are the popular maps in the other regions (US, EU, KR ...) but also let them find quickly the maps they have played to leave comments!

Getting the list!

Bad news, the listing is only available inside the game. And with the anti-hack measures Blizzard is taking, this is not a viable solution to extract them from the client. So we have to find another solution!

Hopefully, there's one. Blizzard is updating a website called Battle.net with the profiles or every player. In the player profile there are his latest 24 games played.

Since we can't parse all the characters (there are more than 1.6 millions as I speak) we are going to parse as much as we can picking them randomly. And we just add +1 for the couple [Map, Date]. As a result for each map we get the an approximation of number of times it has been played.

As you can see there's a hole around September 9, this is a side-effect of the 24 latest played limit. The data has been gathered for 2 days between the 15 and 16. Before the 9 you can see all the casual players that don't play too often and who's 24 limit has not been reached. Between the 11 and 13 the frequent players and after the hardcore ones.

However those artifacts are likely to disappear with a constant spidering.

Does it match?

Now that we've got a lot of data, the question that everyone's waiting ... Does it match the popularity listing!

Calculated Popularity | Position Difference | Real Popularity

As you can see, the top 12 maps are the same with some small ordering differences. However since the order is constantly changing, that's not that a big issue.

In order to get those results about 30 000 players have been parsed and the top popular map Nexus Wars has 2200 points (Real popularity is about 6000). Instead of using the data from the last 12 hours we used the data from the current day and the day before (the granularity of Battle.net listing is 1 day).

Conclusion

It was really hard to know if this method was going to give similar results as the ingame popularity. The only way to make sure of it was to test! I've setup the website scladder.com (recycled domain name) to show the values. However, due to the number of requests needed, I am probably not going to keep the spider running for a long time.

I just showed you that it was possible to datamine websites in order to obtain useful statistics 🙂 I hope you like it!

Prime number recognition is a very hard problem and yet no good enough solution has been found using classical algorithms. There are two ways to get around those limitations: find an algorithm with a better complexity or find a way to compute faster. The first one has already been researched by a large amount of people so I decided to give a shot to the second one.

We are limited by the speed of the electricity, so my idea is to use speed of light to improve speed by a great factor. I've come up with a simple example of how to use it to compute prime numbers.

We set up 2 mirrors with light sources that are directed.

We first set the sensor to the position lower 2

2 had no light so we create a new one that is going to en-light all the multiples of 2

3 had no light so we create a new one that is going to en-light all the multiples of 3

4 is already in the light, we skip it

hasLight(n):
// Sensor placed at lower n that tells weither if it is enlightened or not
 
newLight(n):
// Creates a light that starts from lower n, targeted at the upper n + n/2,
// that first reflects to lower 2n and then to all the multiples of n.
 
isPrime(n):
for i = 2 to sqrt(n)
  if not hasLight(i)
    newLight(i)
 
return not hasLight(n)

This method allows us to recognize prime numbers with light sources, mirrors, sensors and a bit of programming.

Recognizing if a number is prime or not requires to have a lot of lasers and sensors. I don't think that is a viable process, however this could be interesting to do multiplications. You want to fire 2 lights and then see in what point they cross. However there are 2 main problems:

• It requires to have 2 really long mirrors possibly infinite which is not possible in practice. It may be possible to add a vertical mirror in order to work in a bounded area. Yet to know how many times the light hit that mirror.
• We are required either to have an infinite number of sensors. We could have only one sensor that checks all positions sequentially but then we loose the speed of light! What is wanted instead are mirrors in each position that would redirect light to a unique sensor capable of knowing where it came from.

This is an experiment and it is not at the moment near to be faster than actual methods but this is a new way to think about programming. I don't know if anything useful is going to be deviated from this but it shows how to use the light to compute things.

While on holidays, I played that old (bought in the 80's) board game called Fief. After several games I wanted to point at the good and bad things about this game in order to find some general rule.

Fief - Board Strategy Game

Some assets of the game are innovative and worth mentioning.

The resources are really limited. It is common to have limited number of soldiers or houses, but the limitations are often relative to a player. In this game, there is a limited amount of money. After several rounds, there's no money left in the bank and people cannot earn their income. This opens the possibility to organize bankruptcy.

Movement design is clever. The only way to move your army from town to town are Lords. They are special soldiers that can walk 2 towns a round. While moving, they are able to carry any amount of soldiers with them. Once they are well positioned, the Lords allow you to move around the map really fast.

However, that's not a perfect game, the main problem could be summarized with the statement "10 pages rules book". Here are some consequences of that fact.

• Many rules leads to contradictions and unclear statements
• The learning curve is disastrous
• More time spent reading and discussing the rules than playing the game

In order to find a solution, we are going to analyze some facts and get general rules off them.

Could we play without this rule? Yes. Drop it.

In the game, there are 2 types of building that gives resources: Mill [cost 300, give 200] and Press [cost 200, give 100]. Basically, you first buy all the Mills and when there are no left you start taking Presses. These two buildings are just about the same, do not give any kind of reflexion but have to be learned by the players. Removing one building would not affect the decision range of the user and would make the game easier to play.

Ten things doing slightly different things? Merge them!

There are lots of cards but you can never use them. There are offensive cards and their respective defensive cards. Offensive cards are targeted against a player and aren't that common. No need to say that you never have the defensive card when needed. That's about the same for cards that gives money, you either have to be Clergy, have a Fief or be King to use them. Since most of the time you are nothing, these cards are trash. Being given useless card over useless card is a really bad feeling.

A solution would be to transform these useless cards would be to make them generic. What about having a rare card that can counter any offensive attack. As for the money card, it would give money based on the highest rank you have. By changing how to attribute the cards, we could keep the same usage rate. They would be seen like a great reward and as a side effect simplify the game.

Simple rules, great flexibility.

The methodology adopted by the game is: "There's a problem? Add a special rule for this exact problem". What if we let the user the possibility to do it anyway? It will give flexibility and make the game easier to understand! For further thoughts about this philosophy in the web development, i would suggest you to read the free book Getting Real.