Category Archives: For Fun

Upcoming Trip: Japan & New Zealand!

After a busy summer home in the Colorado mountains, biking, running and climbing, my looming trip to Asia is right around the corner. Next Tuesday I fly to Tokyo for 10 days exploring Japan then fly to Christchurch, NZ for two weeks backpacking around the south island! Below is a short list of goals I have for both destinations, be sure to keep checking here to see how I make out!

Japan
New Zealand

With those goals in mind, I will plan to be flexible with my itinerary to hopefully see some seasonal things as well as explore places with less of an Internet presence.  I will be posting here as well as my Flickr as I tour so check back often to see how I fare!

New Toys

Now that I have finished school and can relax for a little bit, I have started playing with my family’s new toy, the mountain board, soon to be paired with the existing kite surfing kite. The mountain board is pretty fun once you get a hang of it but should be more interesting with the kite and some strong wind. I have also been playing with my new Droid Incredible which I am loving (and actually typing this post from quite quickly). I still have quite a bit more to learn but hopefully this summer I’ll get a chance to play some more.

Peace and chow,
Ranok

Posted via email from Ranok’s Ramblings

Computers Like Rectangles

The other day I was at a friend’s house, and while waiting for the oven to preheat, I stumbled across a game I once played as a child, a triangular peg board where the goal is to remove pegs such that there is only one peg remaining. I was thinking of devising a program to attempt to solve the puzzle, much like my programming languages assignment last year to solve a slide puzzle. However, the more I thought about it, the more I realized how attached the conventional computer science paradigm is to rectangular data. It is almost too easy to write a program to play checkers (or at least manipulate the pieces on a board), but it is certainly non-trivial to write a simple and efficient algorithm the maintain the board state. I think it’s rather interesting how the problems we generally have to solve fit rather nicely into their little rectangles, and how few problems require other shapes.

For a solution to the peg board problem, I found this site that documents the author’s process and a code listing. If you’re interested in the game as much (or more) than that the programmatic solution, there are also a number of statistics for possible solutions on the site.

Peace and chow,

Ranok

Off on a Tangent: Calling Conventions

There are many things that we take for granted when using a computer: the operating system, hard ware drivers, and graphical interfaces. By learning about these tools, it gives a new awareness into how much work it takes to get even a simple system working. Computer programmers also take advantage of a number of software components: compiler, linker, operating system, memory management functions and debuggers. There is quite a bit of behind the scenes that goes on even in a simple program like:

int foo(int a, int b) {
return a + b;
}
int main() {
return foo(3, 4);
}

Still has many layers underneath the obvious, the one I want to mention briefly today is the calling conventions. I was curious what happens when you call a function, and looking on wikipedia, I found an article that very nicely shows how many possible things could happen.

Normally in with gcc, when you call a function, the generated code pushes the arguments to the function onto the stack in reverse order, that is, last argument first, and then pushes the address of the next instruction to execute and jumps to the function. That function then can access the arguments and put it’s return value in EAX and jump back to the pushed instruction address. The caller must then clear the stack and use the EAX return value.

However, a way to optimize your code with gcc is the -mregparm=N command, which will put the N < 4 first arguments in registers EAX, EDX, and ECX respectively and push the rest onto the stack. This is much quicker since it requires less memory access. However, you must make sure to compile all your code this way, otherwise you’ll have some strange interactions when the conventions are mixed.

Peace and chow,

Ranok

Back in the Groove

After taking off the afternoon due to a migraine, and napping for a few hours until it passed, I was looking over some old projects, and decided to get motivated to work on my various Erlang hackery projects. I checked out a fresh copy of Open Server Platform on my new computer, and decided to hack on it some more. There are a number of loose ends I’d like to tie up before the 0.3 release, but, before I could get down to coding, SVN get my so frustrated that I could no longer deal with it and switched to git, creating a new repository on Github. I will keep the Google Code repository the ‘defacto’ repository, where the safer code gets committed, but use Github for the more bleeding edge development due to it’s simplified branching and merging (among other things).

In the new git setup, I have two branches (aside from master, which follows the SVN repository): otp and no-otp. The no-otp version is currently the stable code that runs just fine, but doesn’t take advantage of Erlang’s OTP framework. The otp branch is the more cutting edge OTP aware version, which I hope to fully migrate to soon. With full support for OTP, I should be able to use an already existing distribution platform, and more battle tested redundancy.

This evening, I fixed a long standing bug in the example HTTPd where the server would crash when opening large files due to a shortcut I took with first implementing the server. Originally, the server would read the entire file into a string and then send that to the client, as you can probably see, there is a problem when the server tries to read in a 3.9 GB file (my test file). Now, my servlet takes a much more sane approach, read in the file 1 kilobyte at time, sending that to the client before reading more. This new approach works perfectly, though I had to add some messiness for handling CGI/PHP files and different MIME types. I also added support for the HTTP HEAD command.

Peace and chow,

Ranok