A postmortem for Ocean of Code (Codingame AI Contest)

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  • Codingame
  • post-mortem

Every couple of weeks, there is a contest hosted by the folks at codingame.com. This time it was based on Captain Sonar.

Ocean of Code
Ocean of Code

If you just want to look at my statistics for this contest, you can just scroll to the bottom but, then you would miss seeing all the things I did wrong. 😊

Preamble

For the contest, you were in command of 1 ship on a grid and the goal was to have more hit-points than the other ship bu the end of the game. There were islands located all over the map which you had to avoid crashing into. Like all other codingame contest, the game was turn-based, where each turn consisted of you reading the world state information from stdin and outputting your action to stdout. This would be repeated till either only 1 bot was alive or a fixed number of rounds had passed. You also had a maximum of 50 ms to submit your action before you would timeout and die.

There are multiple leagues

  • Wood 2
  • Wood 1
  • Bronze
  • Silver
  • Gold
  • Legend

To pass each league, you need to beat the boss of that league. Everyone starts from Wood 2 and depending on how good their bot fares, they move to the higher leagues. Also, as you move to the higher leagues, extra rules might apply.

For this contest, I decided to use C#. I decided to record my development. I don’t talk but if you are interested in watching me code you can find the playlist here

What Went Right

  • Using C#: It is much faster to write code in C# than C++, especially since its what I am primarily using in my day job.

  • I had already participated in a previous contest at codingame so I was aware of which tools I could use. For other postmortems click here.

    • Working with web IDE is a bit clunky but on the forums, I found a google chrome plugin that allowed me to sync a local file to the web IDE. This allowed me to work in Visual Studio which made for much faster workflow. The plugin can be found here.
    • I already knew I needed some kind of utility which allowed me to combine multiple files into a single c# file which codingame requires. Unfortunately, I couldnt use the existing one I had and had to write a new one. (See What Went Wrong)
    • From earlier contests, I had a python script to help download the game data, parse it and put it into a text file which would be consumed by my program. This allowed me to step through and debug the AI when I could see that my AI was failing to win because of some bug instead of just rely on the stderr stream. Unfortunately, I couldn’t use it as is and had to modify it. (See What Went Wrong)
  • Continuous refactoring enabled me to keep my code readable and isolated the areas that I had to work on.

  • I tackled the simplest things first to make progress. I was able to reach Wood 1 just by having an algorithm that avoided crashing.

  • I isolated the IO into a separate class and made it so that every time I was reading anything from stdin it was outputted to the error stream.

  • I had a few global constants which allowed me to do things like enabling/disabling logging with a single line change.

What went wrong

  • For all my previous contests I had use C++, but this time I used C# which meant that I had to rewrite a lot of my existing tooling.
  • I did not write any tests which made it difficult to have confidence that I was not breaking things as I was refactoring and modifying the algorithm.
  • I did not get to spend as much time as I would have liked on this. With work and other personal commitments, I was only able to spend a few hours on the problem.
  • Even though this a 1-month competition, I started only in the last 2 weeks.
  • I wanted to Livestream/record my development and it took a while to get started. I also could only do it early morning before starting work and while the kid was asleep.
  • I got stuck at Wood 1 and iterative improvements were just not helping. This was by far my worst result in a Codingame contest.
  • I did not write the code in a way that I could easily merge it back to master.

What would I do differently

  • Not change my language of choice because it invalidates all the tooling I have.

Other Notes

  • I did not enjoy this contest as much. I had to write a lot of code before I was able to see any result. Generally, going through the Wood leagues is much easier and the complexity starts coming in Bronze. But, in this contest, a lot of the complexity was in Wood 2 itself.
  • I wonder if this frightened away a lot of beginners

Ranking

League: Wood 1

Global Rank: 1474/2279 (65%)

New Zealand: 1/5

India: 15/42

Feel free to follow me at codingame using this URL.

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