» Archive for the 'programming' Category

Hackabit

Saturday, July 30th, 2011 by Niki

Bit.ly held another Hackathon last night, with the intent of playing around with the data available from 1.USA.gov’s developer resources. We were given JSON data representing which government URLs were being visiting, along with user-agents, location, time and other relevant information.

At first I was more interesting in spending my time on a completely unrelated project – writing OCaml bindings to libsmf, a Standard MIDI File library. My efforts can be found on the OCaml smf library page or on my github.

Soon, however, I started to look around at other people’s projects and decided I should participate. Since I was working on a MIDI library, I decided that the perfect project for me would be to translate the data into MIDI. Using the Yojson library to parse the data and OCaml Portmidi (another MIDI library I work on) to generate MIDI events, I created a simple program that hashed the URL to determine which note to play, and hashed the user-agent to determine how long to play the note.

In order to better share this with other people, I went back to working on the smf library and added in the functionality to allow writing MIDI data to a file. Once that was complete, I added that into my Bit.ly project and created a MIDI file. Using timidity I converted it to an mp3 so I could share it with the internet!

github project page

 

Download the mp3
Download the MIDI

3rd Global Game Jam

Wednesday, February 2nd, 2011 by Niki

Last weekend I attended the 3rd annual Global Game Jam, hosted at NYU. The Global Game Jam is a 48 hour video game development competition – you are given a theme and you have two days to create a game based on that theme!

I arrived a little bit late to the game jam this year, but when I got there people were still forming teams. A friend of mine informed me that this year’s theme was “Extinction.” I mingled for awhile, chatting with old friends and discussing ideas. Groups had already started to form, but none of them had ideas that interested me or they already had enough programmers. My friend (and former co-worker) Yury Pavlotsky was also looking for a team with little success. We discussed our ideas and when we realized we both wanted to create an eco-system simulation we decided to team up. Since we are both programmers we spent a few minutes wandering around looking for an artist to join our team. With only a few “I have a team, but if I have time…” responses we decided to just start coding and worry about the art later.

Working with Yury could not have been easier. We both immediately agreed that we would use Microsoft XNA. We spent only about a half an hour discussing the design elements with almost no conflicts. While most teams were busy arguing over what kind of game they should make, what platform they should target, etc., we were already coding. Our idea was pretty simple – we’d have a grid of cells, and each cell could either be: empty, a plant, an herbivore or a carnivore. The plants would grow and the animals would eat, reproduce and die. The player’s job was to keep the ecosystem in balance.

Each plant/animal had its own stats – how long it lived, how often it reproduced, how much air it breathed, etc. If the air became too CO2 heavy the animals would die, conversely if it became too saturated with oxygen the plants would die. However we found this was extremely difficult to balance. Minor changes would result in huge differences with typical behavior being either everything dying too quickly, or the ecosystem rapidly bouncing back and forth between plants and animals. We ended up taking out the air balance (and later, putting it back it, but only for the plants).

The plants were pretty simple – they would reproduce asexually if there was an empty cell next to it. The animals, however, could move around and needed food to survive. They also needed a mate to reproduce. At first their behavior was totally randomized and based solely on the cells in their immediate area. This stupid behavior would result in the animals dying from starvation or simple not reproducing quickly enough. To fix this I decided that the animals should seek out food if they were starving and a mate if they were at the peak of their reproductive cycle. This involved a simple breadth-first search. What was really interesting, however, was the emergent behavior it caused. Each animal acted independently, and yet we would see flocking/swarming behavior! Groups of animals had the tendency to get hungry together and would all seek out food at the same time.

The search algorithm would cause significant slow down when there were a lot of animals and little food. After some simple optimizations (removing almost all memory allocations in the search) the speed improved but not enough. I eventually added a limit to the number of vertexes it would search. This too led to some interesting behavior – animals could only “see” food that was within a certain distance. Since the animals would tend to group together (due to mating) and would flock together, it would often result in the ecosystem rotating – the herbivores would eat all the plants on one side while the plants grew on the other and would start to “chase” the plants. The carnivores would follow the herbivores in the same manner.

At this point the programming was almost entirely done and we could finally think about art, gameplay and a name. Yury had made some placeholder “programmer” art earlier and we ended up loving the aesthetic. Some of our programmer friends offered to make new art for us but they agreed that the current style was perfect and didn’t really need anything from them. With the art and programming out of the way, we spent the last few hours tweaking the stats for each organism, trying to get it so that it was impossible to create a stable eco-system of just plants and herbivores, and getting it so that the eco-system was just barely unstable with all three (otherwise the game wouldn’t end!). We also needed a name but had trouble coming up with something good. I knew I wanted it to sound kind of “old-school” to match the aesthetic and suggested that our title be an acronym that extinction should be spelled “xtinction”. It was at that point that things went downhill and we took the Juvenile approach: Simulated Environment Xtinction Simulator.

We were done! Now it was time to relax and wait for the demos. There were almost 20 games produced at NYU and each team got a few minutes to show off what they made in front of everyone else. There were a lot of really great games! My favorite was “Ned, you really suck the life out of a room” made by a few friends of mine. Other impressive games were “VS” (also made by some friends), “Goldbloom” (about the death of print media) and “Thawed” (a text adventure about polar bears). After the presentations each team got to vote for the following categories: best overall, most beautiful, best use of theme, wild card and most potential. NYU also had a panel of judges that would choose one game as their favorite. “Ned” ended up taking best overall, most potential and the judges choice. Our game won best use of theme and got an honorary mention from the judges!

The game and all the code and assets can be downloaded from the global game jam website.

Creating an Android project from the Command Line

Friday, May 14th, 2010 by Niki

Android’s developer guide has a section on Developing in other IDEs for those who don’t want to use Eclipse. However the documentation leaves out a few details and all of the examples use Eclipse with perhaps a token paragraph discussing the CLI. The rest of this post will assume that you have already installed the SDK and properly configured it (added the SDK to your path and installed the appropriate SDK components).

The first thing to do is to figure out which version of Android you want to target. Version 1.6 (aka – “Donut”) is a pretty good lowest-common-denominator. Using the Android tool we will figure out the ID for 1.6:

niki@redblacktree:~$ android list targets

Which will give you a list of all the targets available (this depends on which SDK components you have added). My output looks like this:

Available Android targets:
id: 1 or "android-3"
Name: Android 1.5
Type: Platform
API level: 3
Revision: 1
Skins: QVGA-L, QVGA-P, HVGA (default), HVGA-P, HVGA-L
id: 2 or "android-4"
Name: Android 1.6
Type: Platform
API level: 4
Revision: 1
Skins: WVGA854, QVGA, HVGA (default), WVGA800
id: 3 or "android-7"
Name: Android 2.1
Type: Platform
API level: 7
Revision: 1
Skins: WVGA854, WQVGA400, QVGA, HVGA (default), WVGA800, WQVGA432

The target ID for version 1.6 is 2. Knowing that, let’s set up an Android Virtual Device (AVD) for our emulator using the android tool, specifying the target with the –target option and giving it a name with the –name option. We will use the default hardware configuration:

niki@redblacktree:~$ android create avd --target 2 --name donut
Android 1.6 is a basic Android platform.
Do you wish to create a custom hardware profile [no]
Created AVD 'test' based on Android 1.6, with the following hardware config:
hw.lcd.density=160

Finally, let’s setup a project. Again well use the android tool, this time to create a new project. I’m going to create the project in the directory ~/projects/android/hello:

niki@redblacktree:~/projects/android/hello$ android create project --name HelloAndroid --activity HelloAndroid --path ./ --package com.examples.helloandroid --target 2

This will create a new project in the current directory (–path ./) with the name “HelloAndroid” (–name HelloAndroid). It will be targeted towards Android 1.6 (–target 2). It will create a Java source file containing an Activity “HelloAndroid” (–activity HelloAndroid) and will be in the namespace “com.examples.helloandroid” (–package com.examples.helloandroid).

We can now use Apache Ant to build our project:

niki@redblacktree:~/projects/android/hello$ ant debug

This will build a debug version of our project and place the “HelloAndroid-debug.apk” in the bin directory. This application has been signed using a default debug key and is ready to be installed on a device. To do that, let’s fire up the emulator, using the virtual device we created earlier:

niki@redblacktree:~$ emulator -avd donut

Once the emulator has finished booting, we can get a list of attached devices using the Android Debug Bridge or adb:

niki@redblacktree:~/projects/android/hello$ adb devices
List of devices attached
emulator-5554 device

If there is only one device attached, then you can install the application using ant:

niki@redblacktree:~/projects/android/hello$ ant install

Which will automatically remove any previous versions installed on the device and install the current build. Alternatively you can use adb to install the application:

niki@redblacktree:~/projects/android/hello$ adb install bin/HelloAndroid-debug.apk

This will fail, however, if you have already installed a previous version of the application on the device. If that is the case, you need to uninstall it first:

niki@redblacktree:~/projects/android/hello$ adb uninstall com.examples.helloandroid

Note that you must specify the application by the name of its package.

Finally if you have more than one device attached, (say, a phone and an emulator) then you must specify which device (using the name returned from adb devices) using -s:

niki@redblacktree:~/projects/android/hello$ adb -s emulator-5554 install bin/HelloAndroid-debug.apk

Now you can just navigate to the application on the emulator or on your phone and run it! You’ll notice by default it says “Hello World, HelloAndroid!”

That’s the basics of setting up, building and running an application using the CLI instead of eclipse. In the next post I’ll go over release builds and signing your applications.

Android Development without Eclipse

Thursday, May 13th, 2010 by Niki

I have owned an Android-based phone (the G1) for awhile now and have been meaning to develop applications for it since day one. I have finally gotten around to learning how. So far it hasn’t been easy for me: I don’t know Java and I don’t use Eclipse which are the primary development tools for Android.

Fortunately Google released the Android NDK, or Native Development Kit which can be used to program applications in C or C++ and be compiled for the ARM architecture. This introduces new complexities however. The NDK still requires some Java as the compiled code is executed using JNI. In other words I still need to learn a minimal amount of Java and learn how to interface it with native code.

Finally, most of the information online assumes the use of Eclipse. Google provides some tools for creating ant build files but I have found the documentation to be lacking a bit. Through some trial and error I have figured out how to compile the NDK samples and in my next post will present a tutorial for doing so.

Topics so far:
* Creating an Android project from the Command Line
* Signing Android applications

Glow Artisan

Friday, January 8th, 2010 by Niki

A game that I worked on during my time at Powerhead Games was just released: Glow Artisan! It’s a puzzle game for the Nintendo DSi and it is quite addictive. It has already received a number of glowing (groan) reviews:

Nitendo Life 9/10
Game Set Watch

If you have a DSi I highly recommend forking over the $5 to buy it.

Updated dwm patches

Wednesday, September 9th, 2009 by Niki

After becoming increasingly fed up with Ubuntu I decided to reinstall Debian. I had used Debian for a number of years but eventually left it in favor of Ubuntu as I initially saw Ubuntu as Debian with more complete repositories. At first Ubuntu was quite promising however as I diverged from the default install I became annoyed at some of the idiosyncrasies of the system. After attempting to upgrade from Hardy to Intrepid (which requires a graphical installer – and all the directions/tutorials I found online assume you are using gnome/xfce/kde) I realized that what I really wanted was Debian with some additional external repositories.

In the process of setting up my system I decided to update dwm to the latest version (5.6.1). There have been some significant changes to dwm since 5.2 including better multi-head support. Even though I’m not currently using a multi-head system the changes affected my patches and they needed updating. The new diff files can be found on the dwm projects page.

New project: prime number storage

Thursday, July 9th, 2009 by Niki

I have added a new project to the projects page: Prime number storage. When I was in college a friend of mine and I came up with a method for compressing and storing prime numbers. While doing research on our method we discovered that it was already in use.

However I recently decided to implement it anyway, as it was (and still is) interesting to me.

On statements and expressions in OCaml

Friday, May 1st, 2009 by Niki

I first tried to learn OCaml after hearing about it in my Programming Languages course in college. I didn’t get very far beyond the basics at the time for a variety of reasons involving both the language itself and the resources available to me. The problems I had that did not involve the language were not unique to OCaml (except perhaps the lack of available learning material) and were not particularly exceptional. The problems I had understanding the language however were, and the worst offender was without a doubt the semi-colon.

I had a lot of trouble understanding when to use semi-colons and when I needed one of them or two. I’m pretty sure my difficulty with this was not unique either. It seems to me that very few OCaml tutorials or books go into enough detail with this…err…detail and leave it as an exercise for the reader.

Ultimately the problem comes down to the difference between statements and expressions and their relationship to OCaml. There are a few different definitions of both statements and expressions, so for the sake of this post statements are going to refer to stand-alone elements of a programming language that do not return values (that is, they are evaluated solely for their side-effects) and expressions are combinations of values, variables, functions, etc . that are evaluated and return a value.

In an imperative language like C it’s easy to see the difference between the two. An assignment is a statement, an operation is an expression. It follows from this that statements can contain expressions (such as assigning a variable to the result of an operation) and that expressions can also contain expressions (chaining together operators or using the result of a function as the argument to another).

With OCaml it’s not so easy at first. OCaml is a multi-paradigm language and one of those paradigms is imperative programming. A lot of its syntax resembles the syntax of imperative languages like C, but it does not behave like an imperative language. In OCaml there are no statements. Everything is an expression. Everything has a return value. Sometimes that return value is of type unit (as in the case of assignment to a reference). For example, and if…else block in C does not return a value. However in OCaml it does – it’s value is the last expression evaluated within the block. This is why the value of the expressions in both the if and the else block much have the same type.

This brings us back to the semi-colon. The single semi-colon is an operator that behaves similarly to the comma operator in C. It evaluates the expression on the left side of the semi-colon, then evaluates the expression on the right side of the semi-colon and returns the result of the right-side expression (effectively ignoring the value of the left-side expression). So (a;b) would evaluate to b. Since the left-side value is ignored, this is only useful when the left-side produces side-effects (the corollary being that side-effect free OCaml programs shouldn’t use the semi-colon operator).

The only book I’ve seen this in is A Concise Introduction to OCaml which I unfortunately did not come across during my first attempt at learning the language.

New project: data structures

Friday, April 17th, 2009 by Niki

Most of the code that I’ve written in the past few years has been closed-source, proprietary code for my employer. As such I have very little publicly available code to show other people. A few months ago I decided to start working on that by implementing some of the more interesting data structures that I’ve read about. The ultimate goal was to create a Fibonacci heap, which I’ve been meaning to do since I completed the final project for my algorithms class in college. We had to implement Dijkstra’s algorithm on the NYC subway system and a Fibonacci heap can lower the asymptotic bound on the running time.

I started with a Red-black tree as that is a pretty classic and oft-used data structure. Perhaps this endeavor was a little pointless as Red-black trees are usually the data structure used to implement the STL map. In a sense this was both the most useful (because of the frequency with which I use the map container) and the least useful (because it’s already available).

I then implemented two different heaps: a binomial heap and a Fibonacci heap. A binomial heap improves the running time of merging two heaps together (and uses this fact to implement most other operations using the merge) and a Fibonacci heap improves the running time of the decrease key operation – an operation that is frequently used in Dijkstra’s algorithm as well as many other graph algorithms.

The code isn’t as nice as I’d like (there is some debugging code left in, for example) but it was a good exercise and greatly took advantage of template meta-programming in C++.

The project page is here.

12am – a video game developed in 48 hours

Monday, March 9th, 2009 by Niki

I participated in the Global Game Jam with my co-worker Chris a little over a month ago. It was held at the Columbia Teacher’s College. Shortly after we arrived there was a brief introduction to the insanity to come, including a video from the guys that created World of Goo, meant to inspire us (and offering up some sound advice on how to create a game in such a short period of time). We were then given a list of design requirements. The theme of the game was “As long as we have each other, we will never run out of problems.” The game had to be completely playable in five minutes. It also needed to include one of the following adjectives: pointed, persistent or illusory.

After the orientation there was a mingling period where we were able to meet the other participants and form groups. To my relief there was a fair balance of students/enthusiasts and professionals, as well as a healthy mix of programmers, artists and designers. I was afraid that this event would attract too few programmers to be viable but my fears were completely unjustified.

Chris and I decided to stick together, and we eventually found a group of six people to work with, with a seventh on the way. Most were professionals in some capacity although aside from me and Chris, only one other worked in the video game industry. However we quickly realized that seven people was too many, as creative differences and [programming] language barriers were getting in the way. Eventually we split into two groups – our group consisting of four members and another group with three. Our group then split further, with one team member amicably leaving to join another group over creative differences. When we finally resolved the team formation issues there were three of us: me, Chris and Stefan – a Full Sail graduate.

We began designing the game. While we all had similar and complementary ideas we had a lot of trouble coming up with a cohesive design. Eventually we had a rough idea of some basic elements (using time travel to meet the five minute requirement, make a 2D game) and decided to start implementing the basics. I set up a Subversion repository and Stefan and I started coding while Chris dealt with the assets. We used C++ with SDL as our graphics/sound/input library. We ended up using two different compilers (Stefan used Visual C++ while I used gcc) which surprising did not cause any major problems. I worked on the time travel mechanics while Stefan worked on collision detection.

Once we had a code and asset base we went back to design. We ended up dropping the time travel mechanic and using elements of point-and-click adventure games (only with the pointing and clicking – we used the keyboard for input). We created almost a parody of adventure games – showing the consequences of entering someone’s house and looting it (a device all too common in the genre). In the end we had a dark, bleak story of a man who had lost touch with reality and with the one he loved.

With the design finally complete and only a few hours left we got back to implementing the game. By the time the deadline struck we had a fairly presentable (although very incomplete) game. We were awarded “most innovative UI.”

You can download the game and all the source code here, the official game jam website for our game is here.