Saliya's Blogs

import java.util.function.Function;

public class PassingMethodsThatThrowExceptions {

    public static int addOne(String value) throws NotANumberException{
        int v = 0;
        try{
            v = Integer.parseInt(value);
        } catch (NumberFormatException e){
            throw new NotANumberException();
        }
        return v+1;
    }

    public static void increment(Function<String,Integer> incrementer, String value){
        System.out.println(incrementer.apply(value));
    }

    public static void main(String[] args) {
        increment(PassingMethodsThatThrowExceptions::addOne, "10");
    }
}

• an addOne function that takes in a String value representing a number then adds 1 to it and returns the result as an int.
• an increment function that simply takes a function, which can perform the increment and a value then apply the function to the value.
• the main method that calls increment with addOne function and value "10"

    Error: java: incompatible thrown types exceptions.NotANumberException in method reference

public class PassingMethodsThatThrowExceptions {
    public interface IncrementerSignature{
        public int apply(String value) throws NotANumberException;
    }

    public static int addOne(String value) throws NotANumberException{
        int v = 0;
        try{
            v = Integer.parseInt(value);
        } catch (NumberFormatException e){
            throw new NotANumberException();
        }
        return v+1;
    }

    public static void increment(IncrementerSignature incrementer, String value) throws NotANumberException {
        System.out.println(incrementer.apply(value));
    }

    public static void main(String[] args) {
        try {
            increment(PassingMethodsThatThrowExceptions::addOne, "10");
        } catch (NotANumberException e) {
            e.printStackTrace();
        }
    }
}

• Use makrdown aware static blog generator such as Jekyll or something based on it like Octopress
• Use a blogging solution based on markdown such as svbtle
• Use a tool that'll either enable markdown support in blogger (see this post) or can post to blogger (like StackEdit)

Recently I switched to Comcast from AT&T because of an interesting deal on internet. Today I was on my Ubuntu machine in a different network and ran into the issue of not being able to connect to internet. After doing bit of looking into I figured that DNS is not working properly. I was getting a reply that had "hsd1.in.comcast.net" when I tried to do a host lookup (e.g. host -a google.com).

Then when I opened the /etc/resolv.conf I found that Comcast has inserted its nameservers into that and after removing those entries and setting the nameserver to Google's 8.8.8.8 I was able to connect and browse as usual.

Hope this helps someone in a similar situation!

This may not be elegant, but it works !

public static String getPid() throws IOException {
    byte[] bo = new byte[100];
    String[] cmd = {"bash", "-c", "echo $PPID"};
    Process p = Runtime.getRuntime().exec(cmd);
    p.getInputStream().read(bo);
    return new String(bo);
}

Java and C# both have compound assignment operators and the increment/decrement operators. For example see http://msdn.microsoft.com/en-us/library/6a71f45d.aspx for a list of C# operators and http://docs.oracle.com/javase/tutorial/java/nutsandbolts/operators.html for the Java version.

It seems these two step operations, i.e. x op= y, x++, x--, ++x, and --x, are NOT thread safe. It makes sense as these operations require reading the current value of the given variable and then updating it with the computed value. It is possible for threads to interleave between these operations resulting erroneous final values.

There are many ways to guarantee the atomicity in such cases including synchronized blocks, atomic data types such as Java AtomicInteger, and interlocked operations like in C#.

Here are some links that may help,

C# interlocked methods: http://msdn.microsoft.com/en-us/library/System.Threading.Interlocked_methods.aspx

Java atomic classes http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/atomic/package-summary.html

C# library to do threading similar to OpenMP like constructs http://msdn.microsoft.com/en-us/library/dd460717.aspx

A Java alternative OpenMP like parallel constructs https://wiki.rice.edu/confluence/display/HABANERO/Habanero+Multicore+Software+Research+Project

Nothing fancy, just a simple holder to keep my shaver in place. The hole is cut at an 30 degree angle. Initially I wanted to hide the tenon completely inside the mortise, but accidentally route the mortise all the way. Anyway, once fixed the joint is not visible.

Last week I had the opportunity to use Titan, #2 supercomputer in the world as of June 2013, as part of the ATPESC program hosted by Argonne labs. Titan is a Cray XK7 machine and its user’s guide is available here.
The following is a quick start to get Chapel programs run on multi-locale with Titan.

• Modules – the default set of modules is all what you need. You may load PrgEnv-cray/4.1.40 instead of the one loaded.
• Environment – you’ll need to have the following variables exported, usually through ~/.bashrc (in my case I used Chapel 1.7.0)

export CHPL_LOC=/tmp/work/csep65/chapel-1.7.0
export CHPL_HOME=$CHPL_LOC
export CHPL_COMM=gasnet
export GASNET_QUIET=yes
export CHPL_HOST_PLATFORM=cray-xk
export CHPL_LAUNCHER=pbs-aprun
export CHPL_LAUNCHER_QUEUE=batch
export CHPL_LAUNCHER_WALLTIME=00:10:00
export CHPL_LAUNCHER_ACCOUNT=TRN001
export CHPL_HOST_COMPILER=gnu
export PATH=${CHPL_LOC}/bin/$CHPL_HOST_PLATFORM:$PATH
Also, note the values in red need to be changed accordingly. The CHPL_LAUNCHER_ACCOUNT will be the account in Titan to get billed. You can find more information on this in the $CHPL_HOME/doc/platforms/README.cray (search for NCCS).

• Launcher tweak – note this fix is avaialble in Chapel code trunk following revision 21702 (http://sourceforge.net/p/chapel/code/21702/tree/trunk/) so will be necessary only if you are using a release 1.7.0 or older. A minor change to Chapel’s PBS launcher is necessary for these versions to work with Titan due to some upgrade in the qsub wrapper used by Titan. The fix is to change the two occurrences of –l size with –l nodes in $CHPL_HOME/runtime/src/launch/pbs-aprun/launch-pbs-aprun.c
• Compile Chapel – once the above steps are completed use the Makefile under $CHPL_HOME to compile Chapel as usual
• Compile your program – use the chpl compiler to compile your program, which will create two outputs, for example a.out and a.out_real. More information on what each of this means is available in the $CHPL_HOME/doc/README.multilocale
• Start your program – you can use, for example ./a.out –nl 4 to launch your program on 4 locales. Chapel launcher will take care of submitting the correct PBS job for Titan’s job scheduler.

This is pretty much what you need to do and hope it helps!

Nice article on tail recursion with Python at http://web.mit.edu/kmill/www/programming/tailcall.html

Well, it wasn't really a weekend project, but it could have been, hence the title.

Update Aug 2014
 
     Sketchup file at https://www.dropbox.com/s/0qa79linxceagwr/shelf.skp
     PDF file at https://www.dropbox.com/s/5iaalnhmfmkkke8/Shelf.pdf


If you like to give it a try, here's the plan.




The top two are the vertical and horizontal center pieces. The last four pieces are for top, bottom, left, and right dividers. The joints are simply half lap joints (see  http://jawoodworking.com/wp-content/uploads/2008/09/half-lap-joint.jpg).

Just remember to finish wood pieces before assembling. It's much easier than having to apply finish to the assembled product, which unfortunately is what I did.

Never ever use adhesive shelf liners, they suck!

Anyway, since you are here already, here are few tips to help you out.

1.) If you can, use a hairdryer to apply heat while pulling the liner.

2.) No matter how much caution you take, these will always leave a layer of sticky residue behind. This is where it sucks.

2.1) Use WD-40 (http://en.wikipedia.org/wiki/WD-40) and scrape off (using a plastic ruler edge or a small scraper) the sticky mess. You’ll have to do this multiple times and when you scrape use smooth single strokes rather going back and forth.

2.2.) Once you remove bulk of the goo, you’ll still end up having a sticky surface. This is where you need to use coconut oil. Apply oil to a piece of cloth and rub to remove the remaining left over adhesive.

3.) Once all this is done, it’s a good idea to wash away any remaining WD-40 and coconut oil with soapy water and wipe clean with a piece of cloth or sponge.

In case if you were looking to generate histograms in Excel http://support.microsoft.com/kb/214269

Interesting articles on the subject at,

1.) http://blogs.msdn.com/b/shawnfa/archive/2004/05/27/143254.aspx

2.) http://blogs.msdn.com/b/fpintos/archive/2009/06/12/how-to-properly-convert-securestring-to-string.aspx

In summary, a string object is not the best place to keep sensitive information such as passwords, credit card numbers, etc. due to its nature of not being able to lock in one place of memory, immutability (results multiple copies if modified), and possible page swaps (sensitive data now in tmp files) (see 1). Use SecureString as a solution, but sometimes you may still want to get the unsecured string representation as some APIs still don’t support secure strings (see 2).

While at it, you may also like to read about reading a string securely from console,

3.) http://msdn.microsoft.com/en-us/library/system.security.securestring.aspx

4.) http://stackoverflow.com/questions/3404421/password-masking-console-application

Sometime back I played around Mono to get some of our parallel applications running on Ubuntu. These applications were C# based and used MPI.NET.

The following blog post is a great starting point with all the details you'll need. So I'll skip the steps, except to point out couple of caveats you need to consider.

http://blog.biophysengr.net/2011/11/compiling-mpinet-under-ubuntu-oneiric.html

1. automake versions above 1.9 will give you an error when building MPI.NET. May be you can change the make script to work with them, but I found it easy to just install automake1.9 to solve it.
2. You'll need to add /usr/local/lib to your LD_LIBRARY_PATH. Essentially what you need to do is add this path to /etc/ld.so.conf and run ldconfig as root. See documenation from Mono on this at http://www.mono-project.com/DllNotFoundException
3. Make sure to do chmod +x to your dlls