Speed time trials and the Fibonacci sequence

Over the past couple days I've had a little free time at work, so I decided to do an academic experiment to compare computation times between a few languages for generating the Fibonacci sequence.

The languages I originally started with were Ruby and Java, but later expanded to include JRuby and C. Any reasonable programmer would be able to align these and say this is how they expect them to align--and for the most part, they would be right! However, as a thought experiment, why not try it?

I've already said that we're doing the Fibonacci sequence and we'll use recursion first just because recursion is fun and it will really tax the system. Here's the pseudo code for every implementation:


If args.length < 1, print "usage: use an argument for calculation", exit

for (0..arg[0])

print(fib(i))

next



int fib(n)

if n < 2, return 1

else return fib(n-1) + fib(n-2)

So as you can see, this is a VERY simple program. My expectations were that the languages would be ranked like so:

• C
• Java
• JRuby
• Ruby

And I was wrong. Without doing any compiler optimizations, here are the times:

• C - 0m1.778s
• Java - 0m0.933s
• JRuby - 0m11.043s
• Ruby - 3m31.096s

What?? Java is faster than C? That can't be right... can it? Optimizing the C code through the compiler speeds it up some; it's now at 0m0.766s. Shaved off over a second? Huh. It seems to me that something is up, so after consulting the google, I find this article. So Java seems to be helping out a little bit behind the scenes.

Alright, how do we prevent that and still get some good comparisons? Well, I think instead of letting Java do its JIT, I modified the program to get rid of the loop; just do one number at a time. Here are those times:

• C - 0m1.100s
• C (optimized) - 0m0.466s
• Java - 0m0.625s
• JRuby - 0m7.164s
• Ruby - 2m7.298s

Well, Java still seems to be a contender, but that's expected right? We're still calling the same method over and over, so the JIT compiler is bound to still be able to help out. Is that a bad thing? No, you're getting near C-level performance out of the JVM. Pretty cool, actually.

So what? Why am I even testing Ruby? Just to see the performance comparison, really. I've just recently started using it and figured this would be a good comparison of computation time, as well as language syntax. I never expected an interpreted language to be on par with a compiled language--at least for this test.

Ruby is great for lots of things, it's easy to learn, easy to read, but as we see, not great at number crunching. At the same time, putting it on top of the JVM (via JRuby), we get closer to a comparable result with C and Java.

If we use the iterative method for finding Fibonacci numbers, we get these numbers:

• C - 0m0.011s
• C (optimized) - 0m0.002s
• Java - 0m0.102s
• JRuby - 0m0.431s
• Ruby - 0m0.004s

Hmm... Does that make sense? Well, the JVM has to start up which takes some time, so yeah. But Ruby faster than C? I looked a little more at what I was doing in my code. Suspect was the fact that I was printing every number out to the screen. I removed that, in effect just testing looping and some simple math, and here's the numbers: (fib(1000))

• C - 0m0.002s
• C (optimized) - 0m0.002s
• Java - 0m0.099s
• JRuby - 0m0.421s
• Ruby - 0m0.004s

Stepping up the number, Ruby starts becoming less efficient. So an interpreted language can perform reasonably as well as optimized C. Interesting.

In the end, it's a fun test that drives home the point that when you're solving a problem, understanding it and the capabilities and pitfalls of your language makes a difference. Wield your tools appropriately.

Third-party mice && OSX Lion

I was having a tough time getting used to both the Magic Pad and Magic Mouse with OSX Lion, so I decided to go back to my trusty three button. However, with the changes to scroll movement, inertial scrolling and this crazy idea of a third button on a mouse, I had to do some digging to "customize" Lion to work the way I wanted.

First, it's not hard to find the option to turn the "reverse" scrolling off; it's under the mouse preferences saying "Move content in the direction of finger movement when scrolling or navigating." While this isn't the most concise explanation, it's certainly verbose.

Second, I wanted to turn off the inertia when scrolling. This works phenomenally when using either of the Apple products, it doesn't work like I'd like (or what I'm used to; since I switch systems so often). This wasn't quite as easy to find, but luckily, it's out there. This article explains how to change it.

Finally, I like using a mouse that has a thumb button. To use and configure this to my liking, I found some software called USB Overdrive. It has options for all sorts of third party keyboards and mice. This section will help with the various parts of it and how to get it setup for your liking.

Testing with Selenium Grid

This week I tasked myself with finding and fixing memory issues that we've found in the current app I'm working on. Now Java is supposed to be good at reclaiming memory and leaks can be difficult to find.

A little background on the project: it was originally outsourced to a company in India, but has sense been brought in-house for future development and enhancement.

After looking what we were given and fixing initial problems, there were obvious spots that needed refactoring. Moving from the blatant, we started working on the more intricate parts.

Among other things, the application uses Hibernate for persistence. This isn't my first interaction with Hibernate and I rather like it. To call the implementation we were given bastardized might be a compliment. Ripping out the most obscene parts, we were left with a workable solution.

Further refactoring and we had a solution that no longer referenced any of the old code. Usually this is a good thing (tm), but after doing some load testing, it became apparent that we had some memory issues that needed addressing.

After looking at what we were given and what it was changed to, I got a hunch that something wasn't right. Digging through documentation, I had the a-ha moment. We were loading a new SessionFactory for each new database connection. As the documentation says, the SessionFactory should be a singleton. So after making that change, the memory issue was resolved.

Helping find the issue was the load testing environment that was setup. Utilizing Selenium Grid to run tests helped identify the issues we were facing. If you haven't heard of Selenium, I suggest checking it out for doing your acceptance testing. Our environment consists of 5 VMs running Fedora. One has an application and database server and the other 4 run the Selenium Grid. If you have some free time and some extra capacity, check it out.

Fedora 13 & Two finger scrolling

So this took me a while last night... Trying to figure out two finger scrolling in Fedora 13. I've successfully configured touchpads in the past with the HAL policy + .fdi configuration, but in fc13, that's been deprecated in favor of udev and xorg.conf. Here's a really good tutorial on setting up your xorg.conf file with some common params: http://wiki.archlinux.org/index.php/Touchpad_Synaptics

That works for most (and should make your two finger scrolling work just fine), however it didn't for me. Then I came across this post: http://www.cnpbagwell.com/linux/fedora-13-and-asus-eee-pc-1005peb (see the Touchpad section). I didn't dig as far Chris Bagwell did, but taking his suggestion on trying the two finger emulation, everything worked perfectly on my Gateway LT21. The two lines below are what I used:


Option "EmulateTwoFingerMinZ" "35"
Option "EmulateTwoFingerMinW" "8"


Here's a web version of synaptics man page that shows most of the options available for your synaptics driver version: http://linux.die.net/man/5/synaptics. Of course, to see a list of the options that your current driver supports, run this at a term:


man synaptics


As of writing, the latest version is 1.2.2. To update in Fedora run:


sudo yum update xorg-x11-drv-synaptics


Good luck.

Nashville flood

There hasn't been a whole lot of coverage for the Nashville flood, but here's a good representation of what we went through: http://www.boston.com/bigpicture/2010/05/flooding_in_tennessee.html
http://www.nashvilleflood.net

If you'd like to make a donation to the Second Harvest Food Bank, Salvation and Red Cross, visit http://www.wsmv.com
http://www.cfmt.org/floodrelief/

If you'd like to donate time, go to http://www.hon.org

Awesome page to show you how to donate money/time/whatever you have: http://nashvillest.com/2010/05/03/so-nashville-is-flooded-how-can-i-help/

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