We need to find,
	answer
How to get that?
Let’s consider the expansion of
Therefore,
Now let’s substitute values for
	when
	when
…
	when
	when
if you sum them from top to bottom
Taking the sum of arithmetic series,
Therefore,

Special thanks to my friend Jayampathi Rathnayake (http://www.math.indiana.edu/people/profile.phtml?id=jratnaya) for his insight on the approach.

Another good resource http://www.trans4mind.com/personal_development/mathematics/series/sumNaturalSquares.htm

If you don’t have a drill guide like http://www.sears.com/shc/s/p_10153_12605_00967173000P?BV_UseBVCookie=Yes&vertical=TOOL&pid=00967173000 then drilling straight using a hand drill will be a pain and will often result angled holes.

Here’s a simple and elegant (though not precise) solution. You will need a square ruler like http://image.made-in-china.com/2f0j00tvREcekzhJbq/Angle-L-Square-Ruler.jpg. The trick is that all drills have visible center line. Use the square ruler to guide this in a straight line.

When you drill without a guide as shown above, the drill is free to move along both blue and red axes. You can restrict this by using it as shown below with the square ruler.

The square ruler has a flat edge, so when you keep it as above, it will stay perpendicular to the drilling surface. You can rotate the drill to have its center line and the square ruler to be in the same vertical plane as blue axis is. Then, with bit of patience, you can guide the drill while keeping the center line in the same plane. Still the drill is free to move in both directions, but you can use the ruler to guide it very well restricting any movement along red axis.

OK, what about movement along blue axis? This is where you need to have some practice. You can use your eyesight to keep the distance between drill bit and the vertical edge of the ruler constant while drilling to make sure you are not moving along blue axis.

As I said earlier, this is not perfect or highly precise, but when you don’t have any the fancy guiding tools, this works like a charm.

 

Image source for the drill, hand, and wooden piece http://en.wikipedia.org/wiki/File:Drill_scheme.svg

I’ve been wanting a monitor stand for sometime now as the Dell monitor that I am having doesn’t have an adjustable stand. Apparently, these stands cost around $30-40 and it didn’t seem worth the money.

So I ended up building one out of some old furniture parts I had. In the end it turned out to be better than I expected :). In fact comparable to what you can buy online http://www.amazon.com/OFC-Express-Monitor-Stand-Black/dp/B0020LB28Q/ref=sr_1_9?s=office-products&ie=UTF8&qid=1345923737&sr=1-9&keywords=monitor+stand.

Here are some photos.

Finished product	It has enough space underneath to store my files
Top view	Bottom view
Just before I cleaned up the place	My old monitor stand; just a cardboard box from Amazon :)

I’ve been wanting to use an auxiliary input with our 2006 Lexus ES for sometime and found this very neat solution from iSimple http://isimplesolutions.com/product.aspx?zpid=416. After doing some research on other available products on the market I decided to go with this one as it can control an IPod (or any other I* music device) right from the car stereo controls.

Setting up is pretty easy and sound quality is very well indeed! Here are the things  you will need and steps to follow.

Equipment

• A socket wrench and 10mm socket. It’s helpful if you have an extension as well.

• [Optional] A plastic pry bar like the one on below (left). I simply used the one on right and trust me it’s very nice and does no harm to the leather.

Steps

• Shift gear to park  position and push-on emergency brakes.
• Remove the plastic panel around the gear. Here’s a nice pictorial guide on doing this plus removing CD changer (http://www.clublexus.com/forums/es300-and-es330/505772-please-help-advice-i-need-to-replace-my-cup-holder.html)
• Then remove the AC control panel. This has no screws just pulling it out would do. If you need you could use the plastic pry bar.
• Next remove the four 10mm bolts and pull out the car stereo. Here’s a nice video guide for this and previous step (http://www.youtube.com/watch?v=w-0ESCWyz4w)
• To access the back of your stereo you may need to remove wires going for the clock and hazard light switch.
• From this point forward steps are straight forward to follow using the manual provided in the iSimple Gateway at http://www.pac-audio.com/PacProductData/PGHTY1/1_Instructions/pghty1_instructions_020910.pdf.
• A nice set of video demos are at http://www.pac-audio.com/videos.aspx

Tips

• You may need to think where to run your cables. I ran them to the center console box and with some effort managed to make nice installation without any drilling. Just post a comment if you need more information. I wish I took some pictures.
• I used Velcro tape to keep the device attached to the car behind AC control panel.

 

“Yay! I can see my bu** !! … wait, it’s not my bu**, it’s myself !”

If you can come to the last realization that you are seeing yourself then you already understand recursion is natural. If not, the following few examples may help.

Example 1: Is Even?

Zero is even. Any integer N > 0 is even if N-1 is not even.

Example 2: Factorial

Factorial of zero is 1. Factorial of any integer N > 0 is N times factorial of N-1.

Example 2: Length of a List

An empty list has a length zero. Any other list has one head element and a sub list called the tail. So length is 1 more than the length of the tail.

Example 3: Map f() to List S

If S is empty then nothing to do just return an empty list. If not map f() to the tail and get a mapped list. Then add f(head) to the front of that list.

 

P.S. Many thanks to Dan Friedman (https://www.cs.indiana.edu/~dfried/) for his great class of B521 (cs.indiana.edu/classes/b521) at IU, 2009.

----------

About the image; it’s an InkScape sketching of the image I found at http://contortionistsunite.ning.com/profiles/blogs/day-1-3

Chapel supports nesting data parallel and task parallel code arbitrary as desired. This allows you, for example, to spawn asynchronous tasks inside a forall loop. The code snippet below shows code for a case like this where a forall is run on an array of 3 elements. The work to be done for second element is time consuming, hence a new task is spawned to run the timeeater(). Seems straightforward isn’t it? What if timeeater() takes more time than the forall loop? You’d expect forall to wait till all the dynamically spawned tasks to complete, but unfortunately it’s not the case. So if you want everything to be done when you exit forall loop use the construct sync to synchronize.

Try running the code with and without sync and observe the value of result, which should be 500500 if forall exit only after all the tasks have completed.

var d : domain(1) = [1..3];
var a : [d] int = d;
var result : int;
sync forall i in a{
    writeln(i);
    if (i == 2) then {
       begin result = timeeater();
    }
}
writeln("end of forall");
writeln("result ", result);

proc timeeater(){
    var tmp : int = 0;
    for i in 1 .. 1000{
        tmp = tmp + i;
        if (i%25 == 0) then {
            writeln("eating time ", i);
        }
    }
    return tmp;
}

It has been a little while since I started playing around Chapel (http://chapel.cray.com/) language, but could not run anything fun and large until recently. As part of the B524 – Parallelism in Programming Languages and Systems class from Prof. Lumsdaine (http://osl.iu.edu/~lums/), we had to implement Single Source Shortest Path (SSSP) of Graph500 (http://www.cc.gatech.edu/~jriedy/tmp/graph500/) specification. Only then I could realize the easiness of many of the high-level abstractions provided in Chapel compared to other parallel languages or paradigms. Honestly, I did not expect it to work in the first run across a set of machines, but surprisingly it did!

I had a list of URLs that I wanted to download and it was a pain to do it manually. So end up writing a simple shell script and downloading all of them using GNU Wget. Here’s the shell script (modified the one at http://www.linuxquestions.org/questions/programming-9/shell-script-that-read-each-line-separatly-364259/).

#!/bin/bash
# Set the field seperator to a newline
IFS="
"
# Loop through the file
for line in `cat file.txt`;do
 wget $line
done

Finally, an awesome solution to a problem that I’ve been searching for quite a while: how to add an image in a comment to blog post?

Look no further, just visit Spice Up Your Blog on this at http://www.spiceupyourblog.com/2010/12/images-colored-text-blogger-comments.html

Apparently it has just more than adding images like colored text and scrolling text.

See the test comments I made for fun

I've been using Blogger for quite some time and over the years they have improved their Web based blog editor a lot, yet there was some uneasiness always when thinking about editing or adding a post. Anyway, after I got to know about Windows Live Writer I wanted to get it setup with Blogger but it wasn’t successful simply for some reason I couldn't understand “Username or password is incorrect”! I remembered only today that I was using two step verification with Google and that I have to create an application specific password to connect to Blogger. Wish it came to my mind sooner! Anyway, it’s now working fine and if you can read this online that means I made a post successfully with Live Writer.
Few places to note if you are having trouble connecting to Blogger with Live Writer as I did.

1. Blog URL: Don’t forget to use https instead of http
2. Username: Remember to add @gmail.com to your user id
3. Password: As mentioned above, if you are using a two step verification with Google you need to generate application specific password to connect (see http://support.google.com/accounts/bin/answer.py?hl=en&answer=185833)

Feeling a humble joy for being able to make a small contribution to a great resource: Semantics Engineering with PLT Redex, errata on substitution

Thank you Professor Matthias Felleisen for posting it and Professor Amr Sabry at Indiana University for the inspiring course on B522 - Foundations in Programming Languages, which made this possible.

SugarSync public links are great, but unfortunately they've added an intermediate download page instead of the direct download that used to be there (see more on this at http://www.sugarsync.com/blog/2012/01/10/if-you-love-your-public-links-set-them-free/).

May be it was done with good intentions, but it broke all the image links we had in our Web site. Anyway, it seems there's a way around to get images working back in your Web pages without much hassle.

The solution is just add the following to the end of each image link (I know it's bit work too, but way better than having copy images to a local folder and linking them again manually).

old-link?directDownload=true

Update 3/27/2012:

I tried the same trick to put an image to a blog post using a SugarSync public link, but it wasn’t successful. As it seems Blogger’s image retrieving service couldn’t handle the directDownload=true.

http://en.wikipedia.org/wiki/And/or

Want to copy the path of a file to clipboard in Windows without having to open properties window? Just try Copy Path to Clipboard v 1.00 (http://www.softpedia.com/get/System/OS-Enhancements/Copy-Path-To-Clipboard-JA.shtml). It's a pretty neat tool that saves quite a bit of human I/O time :D

Note. It works fine with Windows 7 as well.

If you are using Visual Studio for application development then most probably you may have noticed the lack of built-in refactoring support. At least for me it was so obvious, probably because I was used to the rich environment provided by IntelliJIDEA (http://www.jetbrains.com/idea/) for Java development. So finally did some search to see if there's any third party plug-in for Visual Studio on this aspect and guess what! The same guys who build IntelliJIDEA has a plug-in called ReSharper (http://www.jetbrains.com/resharper/). I had no second thoughts to use it based on my experience and it sure changed my clumsy feeling towards Visual Studio :)

Unfortunately it's not free, but if you are doing open source development they give you it for free. Anyway, the cost isn't sky-high to purchase as well.

අඳුරු වළා ලං වුනා ද
එලිය නුඹේ නැති වුනා ද
සීත අහසෙ රජ වුනා ද
නුඹ ආයෙත් සැඟ වුනා ද

2/22/11

(C) Saliya Ekanayake

If you happen to use MS Word 2007 for equations and wonders why the heck there isn't a shortcut to subscript and superscript then you will like what I just found couple of minutes ago.

If you want to type e1 with 1 as subscript just type e_1. The moment you hit space it will become what you want. To make 1 superscript type e^1 and space. Enjoy!

I wanted to blog about this for a long time and finally it's out today. If you are in the computer science world working in some company or doing research, cubicles will not be a new thing for you. A large room partitioned into blocks of small cubicles and two or more people working nearby are the typical nature of these work areas.

Honestly, I really really don't like this setting. I wonder who came up with this idea of having people sit nearby in the open and work. May be people are thinking that having open cubicles give more freedom to people because they are not physically constrained by walls or doors. But have they ever thought the effect on mind? Does physical boundaries affect the same way to mind? In fact, I think it's totally the other way around. You cannot think effectively when you are in open with others. Essentially what happens is that you are physically free, but mentally constrained.

The truth with everyone, no matter how much they don't like to show it, is that they have unique ways of working optimally. This may include things like clapping and rubbing the hands when your code works and say "Oh! Sh*t" when it doesn't. Not to mention the luxury of thinking silently. How much of these can you do when you are in a professional setting surrounded by others? Also, how much actions of others can you tolerate. Here's one of my personal experience. A person who sat next to me used to sip his coffee so loud and end each sip with the sound "aah". I understand that it's how he likes to enjoy his coffee. That's perfectly fine, but for me that sipping was annoying and disturbing.

So in my view, if you want to work effectively specially when you have to think, open cubicles are nothing but jail to your mind. If you think I am crazy, think of theses (http://www.guardian.co.uk/books/2009/sep/19/books-written-in-prison). These guys were in prison physically, but they had all the "space" in mind to think. No I am not suggesting to go to prison to work :D.

Anyway, another good video on "Why work doesn't happen at work", by Jason Fried from one the TED talks can be found from here (http://www.ted.com/talks/jason_fried_why_work_doesn_t_happen_at_work.html).

My presentation on MapReduce has received some great feedback via Pragmatic Integration. Isn't it really nice to see how somebody who you don't even know benefits from something you have?

I started working with services in Windows world recently and got stuck pretty badly when I tried to host a WCF service in IIS 7. I was receiving errors no matter what solution I tried with Googling. All of them mentioned that I may not have installed ASP.NET properly, but I have installed it properly.

So I was clueless for a while, but luckily found this great article in WCF Tools team's blog, which mentioned that it may be because I installed Visual Studio prior to installing IIS. I did the simple command mentioned there and wow! it worked.

I will post a step-by-step guide in a later post on how to deploy your WCF Service in IIS7.

Recently, I wanted to write the set of value bytes (only them; no key) from the Reduce task of a Hadoop MapReduce program. The signature of the reduce function looked like this.

public void reduce(Text text, Iterator<byteswritable> itr, OutputCollector<text,> output, Reporter reporter)

In the main method I used SequenceFileOutputFormat as the output format. But it turned out that this way I get output as a SequenceFile, which I cannot later read by a separate Java program to extract out the values. May be I am wrong here, but as far as my searching went on, I couldn't find a way to easily do this.

After being fed up with searching I thought of writing a custom FileOutputFormat just to suit my job. So I wrote this ByteOutputFormat class, which simply writes the value bytes as a binary file. So later I can read it using a normal (non Hadoop aware) Java program to extract the bytes.

import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.DefaultCodec;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.RecordWriter;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.util.Progressable;
import org.apache.hadoop.util.ReflectionUtils;

import java.io.DataOutputStream;
import java.io.IOException;

/**
 * @author Saliya Ekanayake
 */
public class ByteOutputFormat<K, V> extends FileOutputFormat {
    protected static class ByteRecordWriter<K, V> implements RecordWriter<K, V> {
        private DataOutputStream out;

        public ByteRecordWriter(DataOutputStream out) {
            this.out = out;
        }

        public void write(K key, V value) throws IOException {
            boolean nullValue = value == null || value instanceof NullWritable;
            if (!nullValue) {
                BytesWritable bw = (BytesWritable) value;
                out.write(bw.get(), 0, bw.getSize());
            }
        }

        public synchronized void close(Reporter reporter) throws IOException {
            out.close();
        }
    }

    @Override
    public RecordWriter<K, V> getRecordWriter(FileSystem ignored, JobConf job, String name, Progressable progress)
            throws IOException {
        if (!getCompressOutput(job)) {
            Path file = FileOutputFormat.getTaskOutputPath(job, name);
            FileSystem fs = file.getFileSystem(job);
            FSDataOutputStream fileOut = fs.create(file, progress);
            return new ByteRecordWriter<K, V>(fileOut);
        } else {
            Class codecClass = getOutputCompressorClass(job, DefaultCodec.class);
            CompressionCodec codec = (CompressionCodec) ReflectionUtils.newInstance(codecClass, job);
            Path file = FileOutputFormat.getTaskOutputPath(job, name + codec.getDefaultExtension());
            FileSystem fs = file.getFileSystem(job);
            FSDataOutputStream fileOut = fs.create(file, progress);
            return new ByteRecordWriter<K, V>(new DataOutputStream(codec.createOutputStream(fileOut)));

        }

    }
}

Hope this would be helpful for you as well.

Couple of days back I made a presentation I made to explain the concept of MapReduce simply. I have attached the slides here for anyone interested. Please note, this doesn't include animations. If you want to get a better feeling feel free to download the original version of this MapReduce presentation.

A good place to learn about .NET naming conventions.

I have been using a color theme for the command line in both Windows and Ubuntu for sometime now and it has been really comfortable for the eyes. So if you feel tired or bored using the white on black try these.

Background Color: #3A4237 (in RGB this is 58,66,55)
Text Color: White

It will give you this feeling of a good old chalk board. Here's a screen capture of how it looks.

My wife, Kalani, has started a blog to post her Sinhala poems. It's nice to see her archive of poems are finally coming up online.

I am waiting to see the poem written for me :D

I wanted to use two computers running separate OSs, yet use the same keyboard and mouse. After searching a bit I found Synergy (http://synergy2.sourceforge.net/index.html). I should say it's one of the most easy-to-use software I have ever encountered. Here are the quick steps (you can read more on their user's guide).

1. Install Synergy on both machines.
2. Setup one machine as the server.
3. Add the machines left, right, top, and bottom of the server (if any).
4. Start synergy as client on those other machines.

That's it and it's working. Only thing is that all machines should be in the same network.

One cool thing is that clipboards of all machines are shared. So copy from one machine and paste in the other is possible. Also it enables you to activate screen saver on all machines at once.

After being able to split the Eclipse windows, I felt the need to split Firefox. Luckily I came across this add-on called "Split Browser", which simply does this for you. It enables you to split tabs both horizontally and vertically. Here's a screenshot of this.

I really wanted the split view feature to be in Eclipse as with most of the other IDEs. In fact, Eclipse has this feature, but doesn't give a visible menu/tool option to do it. The simplest way is to drag the tab containing the source until you can see an arrow mark. Then it will split the view as soon as you let go of the mouse. Here's a nice video I found on how to do this.

http://addisu.taddese.com/blog/split-windowview-using-eclipse/

Here's a screenshot of how it looks.

Great! Now I can stop using mouse for the most part of browsing.

http://support.mozilla.com/en-US/kb/Keyboard+shortcuts

In Sri Lanka, I used to connect to Internet using dial-up connection before ADSL came in. Then I felt "wow! ADSL is fast". But today here in IU, I would say "WOW! what a speed". See the picture below to see why I say this.

I wanted to change the size of the icons in Windows7 desktop as they were bit larger than I like. The solution was a simple one, though I had to do some Googling to find it out.

I just wiped out my Dell Insipiron E1505 notebook and installed Windows7 Professional and Ubuntu 9.10. I had enough of the Windows XP Media Center Edition. I thought of moving to Ubuntu 9.10 as well, just feel the fun.

Unlike in the previous experience with Windows, the Windows 7 performs really well. Regarding Ubuntu, it's better than 9.04 (I was happy with 9.04 as well). The only funny thing is that I had to find drivers and manually install my ATI Raedon X1300 VGA for Windows7. Earlier I used to do this for Ubuntu installations :)

For the moment, these two OSs seems to be a great combination if you are planning to get the best of both worlds.

Pidgin was giving trouble when connecting to my Yahoo account since recently. Today I got to know that it's because of this (http://www.celticwolf.com/useful-information/faqs/26-pidgin-yahoo).

Then I wanted to install a latest version of pidgin on my Ubuntu 9.04. I tried the "how to" given in the official pidgin site (http://www.pidgin.im/download/ubuntu/), but it was unsuccessful. Then I came across these debs (http://linux.softpedia.com/progDownload/Pidgin-Download-6.html) which solved the issue.

Just a quick how-to:

1. Download the i386 (or amd 64) debs
2. Download the two DEB ALL debs
3. Use dpkg -i to install the debs. Start with libpurple-bin_2.6.3-1~getdeb1_all.deb.
Then libpurple0_2.6.3-1~getdeb1_i386.deb (or amd 64 one).
Now move ahead with pidgin-data_2.6.3-1~getdeb1_all.deb.
Next pidgin_2.6.3-1~getdeb1_i386.deb (or amd 64 one)

That's it! no more troubles with Yahoo ;)

See what has happened to the paint and you can understand the defect. Dell, you really need to think more on the paint material :)

After sweating my brain over functional programming in Prof. Daniel Friedman's class over the past several weeks, I got the chance to play with relational programming with miniKanren.

It took me some time to adjust my brain to accept the difference. Finally, I told myself

"Going to the grocer and paying for what you got is functional programming, but going to the grocer and handing over 10$ asking to give whatever that fits is logic programming"

Just a thought :)

Ever wondered what is the purpose of a weird shape hole in your laptop? I did and luckily I found this nice site (http://techplore.com/technology/know-your-connectors-ports-a-visual-guide/) with all the info I needed.

After installing Windows7 on my machine, I went on installing my usual set of software including Google Chrome. But, I wanted to test InternetExplorer 8, which is the default browser, as well. So why wait, I started using it. Wow! I have to admit that it's cooler than Chrome. Why I say this mostly because it has a nice set of customizable accelartors. Also so far it is reliable than Chrome in Windows7. Moreover, it's way better than IE 7, which I consider as a pretty bad version of IE.

My friend, Heshan, has done an interesting work to provide a framework extension to Axis2 which enables Jython based Web services and clients. Read more on his article (http://www.ibm.com/developerworks/web/library/wa-jython/)

Ever wanted to save what you type in your Scheme interpreter? I wanted :). So after a small Google search I found these nice two commands.

I've been watching Britain Got Talent (BGT) for some time now and I've never come across a performer so humble like Eugene.

Really touching video, yet happy for his courage to come forward.

I wanted to run Matlab by logging into the university account remotely from my machine. Everything went fine except for the graphics. Matlab started in no graphics mode.

After bit of a search I found the solution. You have to set the X11 forwarding in you ssh configuration file. Here's how to do it.

1. cd /etc/ssh
2. sudo vi ssh_config
3. uncomment the lines "ForwardAgent" and "ForwardX11". Set their values to "yes"
4. sudo vi sshd_config
5. uncomment "X11Forwarding" and set it value to "yes" as well.

that's it and you are good to go.

Type ssh -X username@domain

To test if everything works fine try running xclock once you log in. It should open up a graphical clock window.

public class Person
{
private String name;
public String Name
{
set
{
System.Console.WriteLine("assigning wow");
Name = value;
}
}
}


public class Hello
{
static void Main()
{
Person person = new Person();
person.Name = "wow";
}
}

I thought of searching for an IDE for Scheme, after being bit lazy to learn Emacs. Lucky enough I found a nice plugin for Eclipse named SchemeWay. It took me a bit of time, however, to configure and set up the plug-in to work as I like.

I have used Ubuntu since it's version 6.04 simply because I felt that it is easy to work with. Anyway, for me, the versions x.04 never gave a good impression. So I used to say "hey! if it's not a x.10 version then it's not what I like". Interestingly, I am finding it is hard to say with Ubuntu 9.04.

Here's a list of things I felt really cool with 9.04.

1. No configuration necessary for the ATI drivers. Yea I had a really fun time configuring stuff with 8.04, 7.10, and 6.10 (Um, I can't remember what I did with 6.04).

2. External display detection is really awesome. It can even arrange the displays in any order I like (e.g. external one on top of default one).

3. Intel wireless card works like a charm.

4. Easy configurations for printers; hmm, I should really admire this.

5. Reliable (so far). Didn't crash, didn't reboot with errors, and most interestingly hibernate seems to work better than in previous versions.

6. Improved graphics.

In summary, I am beginning to like x.04 s as well :)

I found this really useful command in Scheme which helps to trace the function calls, while playing around it.

Say you have define a function named func. Now if you want to trace how it works when you invoke it, just type this.

> (trace func)

The next time you invoke func you will see the trace of function calls.

"...University of Moratuwa in Sri Lanka continues to dominate the field with 22 students accepted."

Wow! am I not happy to see this line in the Internet? I truly am. As a former student of University of Moratuwa, Sri Lanka, I am really happy to see the continuous achievement of its student in Google Summer of Code. To think of the fact that I too was a contributor to this success, makes me happy even more.

Keep up the good work "sharks"

Just hitting "scheme" in the console does no good if you are in Ubuntu 8.04. A workaround is explained here (http://ubuntuforums.org/showthread.php?p=4868292)

Here's the solution in brief:

sudo sysctl -w vm.mmap_min_addr=0

Now run scheme

It has been nearly 14 months since I joined WSO2. Gosh! I feel I joined just yesterday and I strongly believe that it is the wonderful community at WSO2 which made it so pleasant. Today, the time has come to say good bye, yet I am wondering how. It is hard to let go of a place you like.

"No space left on device": Damn, how did this happen?, I told my self. I am pretty sure that I gave enough space for my home partition to carry on with Maven builds at WSO2. Out of curiosity, I issued df -h to see the partitions. Gee, I have accidentally assigned the larger partition to / (root) and smaller one for the home. The only solution is to resize the partitions. After a while, I remembered the great tool that comes with Ubuntu distribution, i.e. gparted.

I booted my machine using an Ubuntu CD and ran gparted. I was very much pleased with its graphical view and was done with my problem in just minutes. Initially my paritions were like,

|------------home----------|--------------/ (root)---------------------------------------------|

After resizing it looked like,

|----------------home----------------------------------------|----------------/ (root)---------|

I was pretty happy with this little tool since it saved me from one hell of a trouble.

Kalani and I got married on 29th May 2009 after being in love with for nearly five years.

WSO2 ESB is a feature rich light weight Enterprise Service Bus. If you are new to what it has to offer, just see the 4 minute flash demo.

WSO2 Mashup Server is another cool product which let you instantly create mashups. See demo for this too.

I was astonished to see this video of Aiden Davis performing on BGT 2009. I really liked George Sampson on last year BGT. Aiden simply is better than him in dancing. Wow! I was thrilled

LTTE brought terror for the last 30+ years in Sri Lanka. They claimed to represent Tamils, but it is a lie to protect their acts of violence. They gave no peace for the Tamils nor for Sri Lankans. The cowardly acts of suicide bombing, child soldiers, and killing of innocent civillians revealed us just one thing about LTTE, i.e. their hatred towards peace.

It is of great pleasure to hear that SL forces have put an end to all this terror by killing the leader of LTTE, the coward Velupillai Prabhakaran. This is the second independence day that we should celebrate.

All the blessings and thanks should go to the brave soldiers and the leader, the President Mahinda Rajapakha for giving hope which eventually became the reality.

I just added a nice label cloud to my blog. Gosh! I now understand that I should have organized my labeling properly :)

It is nice to users themselves trying out new things with WSO2 ESB. Now, Ramanathan has found the steps necessary to deploy WSO2 ESB in JBoss 5.0 GA. Here is the link to his blog entry (http://wso2.org/blog/ramanathan/5318)

I just saw WSO2 Inc. in Wikimapia

Recently I was doing some tiresome debugging with Java using IntelliJIDEA. It was then that I thought that there is a great improvement we can do. This is totally my imagination, so I am not sure on any implementations in the Internet (yet).

The IDEA enables you to put debug points. These debug points may serve in creating a virtual path to traverse through the code. Thus, you are able to quickly jump to the next important point of code by just hitting F9. All this works really well for your debugging scenario. Now, what if you want to debug a different scenario, yet do not want to remove the older debug points? Then you have no option other than to add any new break points for the new scenario along with the older break points. This works okay, but makes the life bit hard since F9 will jump to points which are useless for the new scenario.

So what I suggest is to have a mechanism to define break points separately for each debugging scenario. So when you place a break point you can give it a scenario ID and inform the debugger to follow the break points for the relevant ID. It will be like layers that you find in Adobe Photoshop. You can on/off layers. Similarly we can deactivate a set of debug points based on their ID.

I wonder what JetBrains would think about this :)

Recently, I subscribed to a 3G Internet connection provided by Mobitel. The modem I purchased is Huawei E160. Just like the most other plug-n-play devices this gadget did not include drivers for Ubuntu :). Anyway, I decided to give a try to set it up and voila! it worked.

E160 has two modes of operation. It can act as a GSM modem and a data storage. So when you plug it in under Ubuntu it will attach it under one of these modes. If your network manager is older than version 0.97 then you it will normally get attached as a data storage device. You can see info on this by reading the kernel ring buffer with dmesg -c command (you will need root privileges, i.e. sudo dmesg -c). If it get attached as an storage device use usb_modeswitch to change its mode to a GSM modem.

If everything went well then the rest is pretty easy. You will need to install wvdial (i.e. sudo apt-get install wvdial). Then edit the /etc/wvdial.conf file to include the following settings. Note: these are valid only with Mobitel M3 service in Sri Lanka. You may have to change some settings depending on your service prvoider.

[Dialer Defaults]
Modem = /dev/ttyUSB0
Baud = 3600000
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2
Init3 =
Area Code =
Phone = *99#
Username = ppp
Password = ppp
Ask Password = 0
Dial Command = ATDT
Stupid Mode = 1
Compuserve = 0
Force Address =
Idle Seconds = 0
DialMessage1 =
DialMessage2 =
ISDN = 0
Auto DNS = 1


Now execute sudo wvdial and that's it. You are ready to go online with E160 :D

On the eve of the Sinahala New Year, I was with my parents in our village. All the members of my mother's family were there to enjoy the occassion. Everything went fine until I accidently locked the car while the key was inside. The situation got worse when we found out that the extra key was inside the car as well. 

Just before the Sinhala New Year I got the chance to taste a raw mango with salt and pepper. If you have not tried this before then my advice is do it today itself. Yep, the taste is awesome :)

After relocating ourselves back to the village, I missed the luxury of Sri Lanka Telecom's (SLT) ADSL broadband connection. CDMA was the saviour till yesterday. Suntel, thogh charge a little bit than other providers, gave a fairly good connection (note: fairly good is w.r.t. the available connection speeds in Sri Lanka). 

I just realized the flexibility of WSO2 Carbon when I tried to install Business Process capability into WSO2 ESB, which is based on WSO2 Carbon.

Sri Lankan students gave a huge impact on Google Summer of Code 2008. This is a video by ICTA on that where my good friend Heshan and others giving out there idea on GSoC.

I wanted to test a given string to see if it contains any non word characters in Java. Initially I came up with a lengthy version ;) Then after a bit of search I could simply shorten it.

Version1: regular expression

"\\p{Alnum}*[~!@#$%^&*()\\+=\\-:;<>\\s?\\[\\]{},/\\\\\"]+\\p{Alnum}*"

Version2: regular expression

"\\p{Alnum}*\\W+\\p{Alnum}*"

Here's a nice guide (http://java.sun.com/docs/books/tutorial/essential/regex/index.html) to start with Java regular expressions

The Sun's tutorial (http://java.sun.com/docs/books/tutorial/essential/concurrency/index.html) on concurrency with Java is a great place to start with multi-threading.

Have fun with threads :)

I was searching for a tool to scale images batch wise in Ubuntu and it seems that ImageMagick is just the one for it. Here's how you can get it working as well.

Step1: install ImageMagick

$ sudo apt-get install imagemagick

Step2: go to the images folder and type

$ mogrify -sample 1280 x 800 *.JPG

Here 1280 x 800 is the final size you want and *.JPG is the file set.

To get more info on command options, visit http://linuxuser32.wordpress.com/2007/06/16/batch-image-convert-scale-thumbnail-jpegs-pdf/

I recently came across this nice blog which had a post on locking the screen automatically. Anyway after seeing the comments I found it will be interesting to use Bluetooth to achieve this. I wanted to write some script on my own to get it done. Anyway as an initial step I tried BlueProximity which comes with Ubuntu. Here is a list of steps to get everything working.

1. Install blueproximity:
$ sudo apt-get install blueproximity

2. Pair up your computer with your phone using Bluetooth. You can use System -> Preferences -> Bluetooth to do so.

3. start blueproximity:
$ blueproximity &

You will see the blueproximity icon appearing on your system panel.

4. Configure blueproximity to suit your likings, i.e. the distance after which your screen will get locked, time duration, etc.

That's it.

Anyway it is not kicking unless I can write my own code :D

I started lecturing Data Structures and Algorithms to Level 2 students of the Dept. of Computer Science and Engineering, University of Moratuwa, Sri Lanka. Overall, it is a great experience and I really enjoy it. The bottom line that I understand is that it is only when you start teaching that you understand that you have to learn more ;)

If what comes out of the box does not suit your way of SOA requirements then try out WSO2 Carbon. The ebook (http://wso2.org/project/carbon/making_good_soa_great.pdf) says it all.

Ever tried accessing a shared folder in Vista from Ubuntu? Here are the simple step I followed.

For this example say your Vista user account is vista-pc and password is vista-pw. Also say the IP is 192.168.1.2

----Do the following in your Vista machine----
1. Start/Run secpol.msc
2. Open Local Policies/Security Options, find "Network Security: LAN Manager"
3. Change it to "Send LM & NTLM"
4. share the folder that you want (say movies)

---Do the following in your Ubuntu machine---
1. sudo apt-get install smbfs
2. sudo apt-get install smbclient
3. sudo mkdir /mnt/hd
4. sudo mount -t smbfs -o username=vista-pc,password=vista-pw //192.168.1.2/movies /mnt/hd

That's it :) You can now access the shared Vista folder from /mnt/hd

If you ever encounter an error saying Java heap is not enough, while building a project using Maven, the following content will help to get out of it. Thanks Charitha for finding this.

Sameera, Kalani, Isuru and I developed a Web services security module for the well known Apache Axi2 middleware. The existing security module, Rampart, has issues concerning performance. Therefore, our solution mainly focused on high performance. We used the code name Rampart2 to refer our project, though it is not part of Apache yet. The performance comparison of Rampart and Rampart2 can be found here.

I broke my spectacles and got a new pair from George Gooneratne Optometrists. Guess what? They have taken wrong measurements and I had to visit them again to replace the glasses with correct measurements. After spending about two hours at their lab I finally got my sparkling shiny spectacles. 

 

The day after I was playing basket ball at WSO2 when I got hit by the ball right on my face at a most unexpected time. I was actually catching my breath and I look up only to see something crashing on to me. The shiny new spectacles were broken into pieces and my nose got wounded. The wounds were not that serious and I was lucky not to bleed internally. I found the broken frame of my spectacles and thought, hey that's not too bad because I still have the frame to which I can get a pair of glasses fixed. I put all the pieces into my bag and came home. The next day I was getting ready to go and get new glasses fixed. I collected broken frame and believe me, one side arm was missing. What the hell? I told myself. I searched every possible place I could look into but came up with nothing. Hmm, that's life, I thought and went to optometrist and get a new spectacle fixed. 

 

The next day I was happy with my new spectacles and spent the day peacefully at WSO2. The entire day I was in a meeting and later in the evening I and the others were invited to dinner at an Indian restaurant. The food was okay, but it didn't sound right for me. The next morning I woke up to find that I am suffering from a very bad stomach ache. I spent the entire day at home unable to do anything. The medication came to effect only in the evening. Today is the second day of the very unpleasant "Digesting Error", and there is yet another day to go to end the week. I am expecting what next :)

I had couple of issues with IE and FF3 in Windows and I decided to give it a try with the Buzz: Google Chrome. Amazingly, it's pretty fast than I expected. The next thing I like about chrome is it's simplicity, no stupid buttons hanging all over your browser :). 

Comparing strings is bit tricky :) Say for an example you want to test a String reference against the literal "hello". In simple terms you have a String (say helloStr) and you want to see if the content of that is equals to "hello". You have two choices here,

1. helloStr.equals("hello")

2. "hello".equals(helloStr)

Both will do fine, but which is the better one? I've been using the second form but never thought of the difference (hmm, that's bad ;) anyway people do remember certain things bit later). In one of the code reviews at WSO2 it was revealed. The first form can lead to a Null pointer exception in the case when the helloStr is null. The second option will save you from this since the literal "hello" is not null always and you are invoking a method of a not null object. In this case even if the helloStr is actually null it doesn't matter because it'll only cause the program to check "hello" against null which results false.

If you are checking two String references then you have no option, but always try to invoke the equals() from the most probably not null reference.

Little things do matter :)

After installing FF2 because I was fed up with FF3 I had to setup the default browser in Thunderbird (see my previous post). I was happy after that but today I found that I cannot open any links from Pidgin messenger as well. Argh! I was unhappy again :-/

Fixing this issue, however, was pretty much easy ;) Open Pidgin, go to Tools --> Preferences --> Network. Then you can find a button saying Configure Browser. You'll get a tool window where you can set the command you want to execute in order to open up the browser. In my case FF2 can be started by issuing firefox-2 %s

Just that. It works fine :)

If you are searching for a tool to monitor messages that are exchanged between a client and a server, then Apache TCPMon is one of the best easy-to-use utilities available at zero cost. You can download three different flavors of this utility, i.e. standalone, IntelliJIDEA plug-in, and Eclipse plug-in. To get an in depth knowledge on how to use this nice tool see my blog post at wso2.org.

The following blog posts too give an insight into this tool.

http://charithaka.blogspot.com/2008/08/how-to-use-tcpmon-inside-eclipse.html
http://www.keith-chapman.org/2008/07/using-tcp-monitor-to-debug-web-service.html

I wanted to get the Internet connection to my notebook. The Internet facility is given by a CDMA service. So it's one machine only thing. That's bad because I need it to be given to two machines. Luckily I found this nice way of doing it from Dr. Sanjiva's blog. I'll try to find a pocket router similar to the one he has used and give it a go soon.

Anyway if you want to know about how to setup IP forwarding see the following links.

http://www.ducea.com/2006/08/01/how-to-enable-ip-forwarding-in-linux/
http://www.linuxforums.org/forum/linux-networking/64083-simple-ip-forwarding.html

I wanted to remove FF3 (Firefox 3) and install FF2 in Ubuntu because some of the web applications didn't work well in FF3. After doing a apt-get remove for FF3 and an apt-get install for FF2 I noticed that in Thunderbird when clicked on a link in a mail, will not open up a browser tab. So the hunt began :)

The solution was to tell Thunderbird the path of the browser to open. You need to create user.js file inside your ~/.mozilla-thunderbird/xxx.default/ (the xxx means any weird set of letters and numbers, e.g. 20art4c7). Type (or edit the path as to suit your browser) the following lines into that file and save it.

user_pref("network.protocol-handler.app.ftp","/usr/bin/firefox-2");
user_pref("network.protocol-handler.app.http","/usr/bin/firefox-2");
user_pref("network.protocol-handler.app.https","/usr/bin/firefox-2");

That's it :)

Apache Axiom, which is the popular open source StAX based XML infoset model, supports XPath out of the box. If you ever want to know how to use this feature, WSO2 Oxygentank has a very nice tutorial.

The tricky part is, how to work with Namespaces? To get an idea on to the matter consider the following XML document.



The following code fragment will retrieve the ns1:c1 element and the two ns2:color attributes of each element.

// root is the document
OMElement root = builder.getDocumentElement();

AXIOMXPath xpath = new AXIOMXPath("//a:c1");
xpath.addNamespace("a", "http://namespace1.com");
OMElement c1 = (OMElement)xpath.selectSingleNode(root);
System.out.println(c1);

xpath = new AXIOMXPath("//@b:color");
xpath.addNamespace("b", "http://namespace2.com");
List colors = xpath.selectNodes(root);
System.out.println(colors.get(0).getAttributeValue());
System.out.println(colors.get(1).getAttributeValue());

The important line in this code is the xpath.addNamespace(prefix, uri) method. This prefix doesn't have to be the exact prefix used in the actual document (which in fact is not known in most cases).

That's it, have fun with Axiom :)