I just entered the Netflix competition. After 6h and many attempts to download the Prize Dataset, finally I have it. It is large (~700MB) tarball containing some instructions, qualification file and another tarball (why?). I have spend some time looking at raw data and trying to understand the data format. My initial thoughts is that the appropriate tools for the problem is some mix of Python + C and probably MySQL for data storage.


Graphs beauty

This is some recycled (October 05, 2006) post from my older blogs. I am currently working on some graph rewritings stuff. It all begun with the desire to create new language based on higher order rewritings (and there is some implementation of the language that is intended to be used for genetic programming experiments).

Here are some first experiments on Graph Rewriting. The process starts from random graph i.e. randomly connected vertices and applying rules on graph produces the final graph.

Initial graph:


After 10000 rewriting steps with quite random rules for rewriting:


It is easily visible that some small stable forms appear. They solely depend of the rewriting rules that form cycles or in case of termination — non reducible structures.

And another view of the same graphs (other layout) :


And finally some rewriting with arrity 2:


All images are produced with GraphWiz. The rewriting is done on Erlang based program and appropriate custom tools for producing Dot files for GraphWiz.

Very inspirational and worth watching.

“The Most Important Lessons Learned as An Entrepreneur”

“…I think that it is more important to do what you have passion about…”

And: “What Drives Me”


  • First of all: Solve real problems. You want to change the world, isn’t it?
  • You need a blocknote. Write every idea, meaningless ones too. Good ideas have the right time to be executed. On the other side you will be amazed after some time passed how you mind changes.
  1. Children’s purity of mind. Find children and ask them one simple question: “What is wrong with this world and how to fix it”? Write everything you listen and read it every time you have no ideas.
  2. Solve real problems. Go find some people that do not use computers (and Internet) at all, probably this can be some older relatives. Ask them: “What is the biggest problems you encountered in life”. Write answers on paper and think about them for a wile.
  3. Ask women. It looks like that most of the startup founders are men. This leads to biased view of the world. Women have better understanding of everyday problems.
  4. and 5. There is too much bad things in the world: War, Crime, Starvation, …. Solve one of them. You want to change the world, isn’t it?

Update: I haven’t tried all those tips myself :). I have asked relatives and friends only, but writing in this blog my ideas become clear and it is inspirational for new ideas too.

Red Cat

I have always considered to use Red / Black color palette for my web site, at the same time I was trying to think about web accessibility issues. One point from Startup School notes grab my attention “The web is blue (red-green colorblindness)”. Little research gives me some insight about something I have never considered – color blind users. I suggest this nice article about “Creating Accessible Web Sites” at Penn State University site.

Here are some excerpts:

  1. Do not rely on color codes alone to provide information.
  2. Avoid contrasts of red and black, since some color blind users do not perceive reds.
  3. To ensure that color contrasts are visible to the most viewers, use a color blind simulator. Having enough contrasts in darkness is important for low vision and color blind users.
  4. Adjacent areas of brightly colored hues also cause difficulties for normal-vision because of “color vibration.” (Something that I noted myself for Red-Green combination)

And my suggestion: Do not use 10px font size (at least 12px). It may be ok when page is viewed in some browsers and on CRT screens but on my 15.4 laptop make impossible to read long texts without my eyes start to tear.


I am just reading the XHTML 1.0 specification and remembered the dir=”rtl” attribute. As I intend to create web site that have to support international users it is important to think about support of multiple languages, and as you probably know there are at least two languages that are written from right to left. http://www.w3.org/TR/html4/struct/dirlang.html#h-8.2 If one page is designed for LTR orientation and is used with RTL orientation some elements of the page can appear in unexpected places. So lets try some examples. I will use the Google Translation tool and convert some English pages to Arabic for example.

Let start with the Y-Combinator News site side-by-side comparison:

Y combinator EnglishY combinator Arabic

It looks very nice and elements are mirrored as expected but lets try another site – del.icio.us:


Some elements overlap but most content is shown as expected. Finlay i have tried this on my site and some changes have to be done in the page design in order to properly reverse text orientation if RTL language orientation is used.

The evolution of ideas

Every startup starts with some initial idea. I have my idea too. But ideas evolve and evolute. Evolution have two basic steps:

  1. Innovation
  2. Selection

Every day and every moment when I read something or surf the web, spontaneous ideas pop-up. These ideas extend my initial idea in different ways. So  there is innovation. But selection occurs in very limited way — My opinion of what is possible and what is good. The only good selection is the opinion of users. As it is written on other places and by other people: The best strategy for startup is to create some working prototype of the initial idea and to go public.

Each time when new ideas pop-up develop them as extension to the basic idea and let the users decide if it is worth. Selection force of the users is the evolution force that drive the product in the direction of success.