Polo's Blog

The Best, Easy, Delicious Desserts for Potluck Party

2012-01-14T16:05:00.000-08:00

I didn't like potluck parties. I didn't like how my home-cook dishes look like. They're just not appealing.

One day, I decided I had to fix this. I wanted to learn to make one thing that I could bring. Preferably something that tastes delicious, easy to make, *and* unlikely that other people would bring.

So I found this 5-star Brownie Chocolate Chip Cheesecake recipe.
It needs very few ingredients, and you basically just mix them together, and it tastes fantastic. Brownie bottom layer, plus cream cheese top layer filled with chocolate chips. Yummy. None of my friends could resist. (Mr. V, you should try it, but don't eat so much. Watch your tummy.)

This Christmas, I learned another recipe: Rice Krispies Treat. It needs only 3 ingredients, and 10 min to make (really 10 min, unlike other recipes that lie). Delicious. A good dessert to make when I don't have much time. There's Kellogg's version, but I like my friend's ingredient proportion better:

1/4 cup butter
4 cups marshmallows
5 cups Rice Kripies cereal

Pittsburgh (Being Grad Students)

2012-01-13T01:37:00.000-08:00

Before I came to Pittsburgh for grad student, someone told me there's nothing to do here. And I would freeze to death.

Well, it's certainly different from Hong Kong. But it's a great city. It's medium sized, and you can find a bit of everything, without the craziness of big cities.

First off, CMU has a diverse student population, with students coming from every parts of the world. I haven't counted, but I'm sure my friends come from more than 20 counties. (Just counted, it's roughly 25!)

Pittsburgh has a fantastic football team (Steelers) and an ice hockey team (Penguins). Ahem, and a baseball team, the Pirates. Sorry to say, but the Pirates hasn't been doing that well. Yet, I have only been to Pirates games. Their tickets are cheap.

Whoever says Pittsburgh is cold lies. Don't listen to him. Or her. I have traveled to other cities in the states that are much colder. Try those cities north of Pittsburgh closer to the lake, and you'll know what real cold is! And of course there are even colder ones further north. And it actually doesn't snow that much in the winter. But I never have to shovel snow.

The nicest thing about Pittsburgh is perhaps its cheap housing. As a grad student, I could have afford to buy a house. Though I didn't. And I regret. Many of my friends bought those. Good investment indeed. The Pittsburgh housing market wasn't affected much at all in 2008. People here really buy houses to live in them.

More later.

Steamer instead of iron (Being Grad Students)

2012-01-11T13:59:00.000-08:00

No one likes to iron clothes. It takes so much effort and space. Clearing space in my tiny apartment so I can open up the ironing board is already a chore. Then you warm up the iron. All you want is to just iron one shirt!
Then lately, I learned of a much better alternative -- using a steamer! No ironing board needed. It's fast to heat up the steam (and it only uses water). It has a small footprint. And since it stands upright, you can hang clothes on it. Plus, you can use it to sterilize curtains and other things. Handy.

Decorating student apartment (Being Grad Students)

2012-01-09T11:33:00.000-08:00

If you're like me, a grad student renting an apartment, chances are that you have some rather bare (and boring) walls, because your landlord (or landlady) warned you not to hammer any nails, or they will take a big chuck out from your security deposit.

How do you hang a clock then? What about some frame photos?

I found some fantastic "command hooks" by 3M which can be removed from the wall cleanly. No glue left behind. They also won't pulled wallpaper (unless it is peeling anyways). 3M also sells strips for hanging pictures, among other "command" products.

Thumbs up.

Choose conferences with nice locations (Being Grad Students)

2012-01-08T09:59:00.000-08:00

One of the nicest being a grad student is you get to travel, often "for free", to conference held at great places (e.g., Sydney, Paris, Hong Kong, etc.).

Picking such a conference could motivate you to work hard for a paper. :-) So choose your conference wisely. After all. If you have some good work that you can submit to similar conferences that have comparable reputation/prestige, which conference would you send it to? The nicer one of course.

Just remember to check with you advisor that it's OK with him/her though.

Cut your own hair (Being Grad Students)

2012-01-07T22:00:00.000-08:00

When I was little, my father cut my hair. Then I came to the states for grad school -- no one cut my hair anymore!

Going to a hair salon in the US can be so expensive. The costs add up really quickly. So I thought about doing it myself; I remembered my father saying "it's a piece of cake" cutting my hair. How bad could it be if I did it myself?

Very bad, when I first started, a few years back. I bought a cheap Wahl hair clipper (like this one), and I hated it, even though it's a 5 star product.
1) It has a long cord, which often get in the way
2) It's really awkward holding it to cut the side or the back of my head -- just try using your right hand to scratch your left ear from behind your head, and you'll know what I mean.
3) It's a big hassle having to keep changing the "length guides" for different hair lengths.

Apparently, you need something different when you cut your own hair. I found this Philips hair clipper recently, which solved all the above problems!!
1) It's cordless.
2) It has a rotating head, so you can hold it sideway when you cut your hair on the side or the back of your head
3) It has a "zoom ring" that lets you change the cutting length from 30mm (about 1.18 in) down to super close shave. No need to fiddle with the millions of "length guides"! (Well, technically, there are still two guides, one for the longer lengths, one for shorter lengths.)

I love this clipper. Great for a quick fix.

For those of you (men) who haven't cut your own hair before. It's very easy (assuming you use this Philips clipper, and you just want to style your hair a little). Here's how:

1a) Pick the longest length you want your hair to be (e.g., 30mm), and run the clipper through your whole head.
1b) If you want to style the top part of your hair (e.g., for parting, or styling), leave that part longer (or don't cut that at all) for later.
2) Pick a shorter one (e.g., 25cm) and run it along the areas close to the ear, and the back of your neck.
3) Repeat step 2, with even shorter length if desired. The key is to "blend" different lengths of hairs.
4) To add "layers" to your hair (to make your hair more "choppy" and to fine tune it to frame your face), use a pair of scissors, and cut "into" your hair like this.

Of course, if you need a really clean cut, or fancy style, you'll have to go to a hair salon.

Grocery shopping, folding t shirt (Being Grad Students)

2011-01-05T11:48:00.000-08:00

1. When grocery shopping, instead of doing all the math in your head about which brand of food (or toilet paper if you may) is cheaper, you can often look at the tiny text close to the prominent sale price. For food, it's often stated as $XXX per ounce (and for toilet paper, $YYY per roll). This save you some brain cells, and some gold coins in your wallet.

2. Fold a t shirt in 2 sec. (This makes the chore slightly more bearable.)

http://youtu.be/An0mFZ3enhM

Creating decorators in the Prefuse framework

2009-08-13T20:03:00.000-07:00

I'm working on some graph visualization using Prefuse, and I want to allow the use to select nodes in the graph by dragging a marquee. In addition, I want to show a tiny black square indicator at the top-left corner of a selected node. The image on the left is what I eventually got.

I wanted to use the Decorator design pattern provided by Prefuse to add the square indicators. Conceptually, the steps are:

programatically selects a subset of the nodes in the graph
applies the desired decoration on those subset of nodes

But in the actual implementation, these basic steps unfold into much more complex steps:

creates a "focus group", of type "DefaultTupleSet", to the "visualization" object, using the method visualization.addFocusGroup(); you'll need to give this newly created group a name. This group (which is a "tuple set") is precisely the data structure that you use to store the selected nodes
look at this example on how to create a control that lets you draw the rectangle marquee, which will put the selected nodes into the "focus group" that you created in step 1.
now comes the nontrivial part -- creating the "decorators", which are objects created to decorate the selected nodes. Programmatically, you call visualization.addDecorators() to create this new group of decorators. Again, you give this decorator group a name.
creates a layout action to continously relocate the indicator so that it always stay at the top-left of the node
creates a renderer to render the tiny square. I think we can use a ShapeRenderer instead so this step could be skipped.

NEVER USE "graph.nodes.xxx.yyy.zzz" AS A GROUP'S NAME. IT BREAKS PREFUSE. I haven't had the time to figure out why, probably because of some of its internal parsing error, but this kind of names break Prefuse. I learned about this the hard way; wasted 4+ hours.

Using BitSet or BitVector to store a set of integers

2009-05-25T14:53:00.000-07:00

When programming with Java, we typically use HashSet to store a set of Integer, if we want to keep track of which Integer has been used and which hasn't. When we need to store millions of Integers, HashSet can be too slow, and it may take up too much memory.

Java's BitSet and BitVector from COLT are great alternative; they are MUCH faster and consumes way less memory. For example, to store 20 million integers, both BitSet and BitVector only use about 2.5MB and take only, respectively, 0.67s and 0.27s (which means BitVector is the fastest) to set and get all of the values once. using HashSet, it takes ~962MB, and 6.3s. This is more than 380 times of memory saving, and ~20 times speed up.

One "disadvantage" for BitVector is that it's size can't dynamically scale, but you can always fake it by manually growing or shrinking the set via setSize(...)

I can't figure out why Java's HashSet implementation uses so much RAM; I tried to reduce the size to 2 million, and that uses 100MB, approximately 1/10 of the size when having 20 millions. So this means indeed the Java implementation is memory-hungry. I'm sure there's some way to cut down the memory consumption, but I haven't spent the time to investigate.

Speed Comparison of: (1) Java's built-in HashMap, (2) Trove's TIntIntHashMap, and (3) Colt's OpenIntIntHashMap

2009-05-09T22:29:00.000-07:00

Finally get to do a comparison among several popular Java HashMap implementations:

Java's built-in HashMap
Trove's implementation for primitive types
Colt's implementation for primitive types

Not too surprisingly, Java's built-in implementation is the slowest, and consumes the largest amount of memory among the three, since it stores objects instead of primitive types (e.g., instead of storing the number 3 as an int, it stores it as an Integer). What WAS surprisingly, however, was that Colt's implementation was SO MUCH faster than Java's implementation. For example, for a int->int hashmap, running 10,000,000 puts() with Colt took less than 1/3 of the time. Running 10,000,000 gets() took less than 1/6, and 10,000,000 containsKey() less than 1/5! This is some substantial timing saving. This time-saving advantage is still there, even when we use a int->float[] hashmap.

Memory-wise, the primitive implementations from Trove and Colt don't save us that much. For int->int hashmap, both Trove and Colt save us about 30% of memory, but for int->float[] (each float[] value has length 5) save us less than 10%. Nevertheless, there's still some saving.

Since I need to deal with large data sets, where it's common to use hashmaps with millions of entries, I'll use the Colt implementation from now on, for both it's impressive time saving and (slighly) lower memory consumption.

Here's the code I used for evaluating int->float[] hashmap. To get the timing and memory consumption for one implementation, comment out the other two that you DON'T want. You will also need to pass in these arguments to the VM, so enough heap memory will be alocated "-Xms1200M -Xmx1200M".


import java.util.HashMap;

import cern.colt.map.OpenIntIntHashMap;
import cern.colt.map.OpenIntObjectHashMap;
import gnu.trove.TIntIntHashMap;
import gnu.trove.TIntObjectHashMap;


public class Compare {
 
 public static void main(String args[]){
  
  System.out.println("1st line: time used(s)\n2nd line: heap memory used so far(MB)");
  
  int n = 10000000;
  
  long startTime = System.nanoTime(); 
  long startHeapSize = Runtime.getRuntime().freeMemory();

  
  // BEGIN: benchmark for Java's built-in hashmap
  System.out.println("\n===== Java's built-in HashMap =====");
  HashMap jIntIntMap = new HashMap();

  System.out.println("\n-- " + n + " puts(key, value) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { jIntIntMap.put(i,new float[]{0f,1f,2f,3f,4f}); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  
  
  System.out.println("\n-- " + n + " gets(key) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { jIntIntMap.get(i); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  

  System.out.println("\n-- " + n + " containsKey(key) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { jIntIntMap.containsKey(i); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  
  // END  
  
  
  // BEGIN: benchmark for Trove's TIntIntHashMap
  System.out.println("\n===== Trove's TIntIntHashMap =====");
  TIntObjectHashMap tIntIntMap = new TIntObjectHashMap();

  System.out.println("\n-- " + n + " puts(key, value) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { tIntIntMap.put(i,new float[]{0f,1f,2f,3f,4f}); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  
  
  System.out.println("\n-- " + n + " gets(key) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { tIntIntMap.get(i); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  

  System.out.println("\n-- " + n + " containsKey(key) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { tIntIntMap.containsKey(i); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  
  // END     
  
  // BEGIN: benchmark for Colt's OpenIntIntHashMap
  System.out.println("\n===== Colt's OpenIntIntHashMap =====");
  OpenIntObjectHashMap cIntIntMap = new OpenIntObjectHashMap();

  System.out.println("\n-- " + n + " puts(key, value) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { cIntIntMap.put(i,new float[]{0f,1f,2f,3f,4f}); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  
  
  System.out.println("\n-- " + n + " gets(key) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { cIntIntMap.get(i); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  

  System.out.println("\n-- " + n + " containsKey(key) --");
  startTime = System.nanoTime(); 
  for (int i = 0; i < n; i++) { cIntIntMap.containsKey(i); }
  System.out.println( (System.nanoTime() - startTime) / 1000000000.0 );
  System.out.println( (startHeapSize - Runtime.getRuntime().freeMemory()) /1048576.0  );  
  // END    
  
  
 }

}

How to write a great research paper

2009-01-23T12:33:00.000-08:00

A great guide by Simon Peyton Jones

Embedding web browser in Java application

2008-12-03T13:40:00.000-08:00

I found this NativeSwing library an excellent library for embedding a web browser in a Java application, seemingly easier to use and much better documented that JDIC.

Primitive Java Collections (primitive hashset, etc.)

2008-11-25T22:16:00.000-08:00

Java's built-in collections such as hashmap, hashset, etc are not efficient when you have a lot of data (e.g., 1 million of items), it's because everything in the hashmap (i.e. its keys and values) and hashset (i.e. its values) are stored as objects, which are expensive to store and access. So if you want to store, say, 1 million int in a hashset, use a primitive hashset instead, such as Trove, or COLT. They seem to be some of the best primitive collections. But I haven't compared their performace (memory consumption and access speed) so I don't know which one is better.

Downloading full CiteSeerX data

2008-11-18T18:49:00.000-08:00

Here is, in my opinion, the easiest way to download the full dataset from CiteSeerX. (Note that CiteSeer is the older version, which is no longer updated.)

Steps for downloading the full dataset from CiteSeerX:

Download and extract the "Demo" from http://www.oclc.org/research/software/oai/harvester.htm
Go to the directory of the extracted files, type the following command to download the full dataset of CiteSeerX to the file "citeseerx_alldata.xml"
java -classpath .;oaiharvester.jar;xerces.jar org.acme.oai.OAIReaderRawDump http://citeseerx.ist.psu.edu/oai2 -o citeseerx_alldata.xml

I also wanted to thank Dr. Lee Giles from the CiteSeerX project for pointing me at the right directions to obtain the data and recommending me to try some Perl harvesters (though I didn't eventually use them).

People won't buy what they don't understand

2008-02-22T13:00:00.000-08:00

"People won't buy what they don't understand"
A great sentence! That's why we need to write plain English. :-)

Two nice Java libraries for visualizing and exploring graphs (networks)

2008-02-13T22:12:00.000-08:00

Prefuse (http://prefuse.org/)
JUNG (http://jung.sourceforge.net/)

Main observation:

JUNG is designed for graphs, while Prefuse is designed for many different types of data (which include graphs).

JUNG has graph operations and algorithms that Prefuse doesn't have

JUNG seems to be better documented
JUNG seems to be more scalable
Examples from Prefuse seem to be more pretty
Prefuse provides nice interactivity and cool animations

Free WPF DataGrid from Xceed

2007-08-14T12:33:00.000-07:00

Exactly what I need for my current project. So glad I found this great stuff from Xceed before I try to build one myself! (URL: http://xceed.com/Grid_WPF_Intro.html)

Get the keywords associated with a result item returned by Google Desktop Search

2007-08-12T00:56:00.000-07:00

I've been programming with C# and Google Desktop Search (GDS) API for quite a while. Today, when I was browsing the Interop library of GDS (Interop.GoogleDesktopAPI.LIB) in Visual Studio 2008, I found that it's actually possible to obtain the keywords that Google Desktop has identified out of an indexed item. This hasn't been documented by Google GDS API guide yet. (I'm using GDS version 5.1.0707.23222-en-pb.)

Just call the function GetKeywords(int numKeywords, bool includeWeight) of any IGoogleDesktopQueryResultItem3 object and you'll get the keywords as a list of strings. Even better, if you set the input parameter includeWeight to true, then not only will you get the list of keywords, but following each keyword, you'll get the ranking score of that keyword as well.

A sample output for GetKeywords(10, true) is as follows:
papers:10.78 workshop:9.62 layout:9.01 university:8.18

Setting the input parameter 10 asks GDS to return the first 10 keywords, if there are more than 10. Notice that the keywords are always ranked by the ranking score in descending order.

One last thing, it's important to cast a result object to IGoogleDesktopQueryResultItem3, since only this version 3 result object has the GetKeywords() function.

Re-enabling the Aero glass effect in Windows Vista

2007-08-03T11:21:00.000-07:00

If you're using Vista with a nVidia graphics card and you want to update the graphics card's driver, the chances are that after upgrading, you may loose the Aero glass effect (the semi-transparent and blurred windows title bars). That is, Vista may all of a sudden stop using the graphics card's hardware acceleration to draw windows and the desktop, causing the windows' backgrounds to become opaque and the "Switch between windows" 3D effect (the fancy-looking windows switching animation when you press Windows+Tab) to become disabled.

If that hasn't happened to you, then congrats! It happened to me on two computers, one desktop and one laptop. Fortunately, the solution is simple. Just go to "Control Panel -> System And Maintainence -> Check your computer's Windows Experience Index base score" and click "update my score". After the new score has been calculated, you'll get back your graphics acceleration... Don't know why, but it works! :-)

WPF: getting a data-bound data template and the items within it

2007-06-28T12:11:00.000-07:00

I'm so happy to find out about Rich Strahl's post on how to get the items within a data template that is data-bound to, say, a list box.

It turns out the only way to get an item inside a data template is to programmatically go into the UI hierarchy of the template... not elegant at all!

The best tutorial about data binding in WPF

2007-06-26T22:32:00.000-07:00

It turns out that Microsoft's MSDN has the best tutorial around about how to do data binding in WPF. Everything is explained clearly; the diagrams, tables, and examples are just perfect. Double thumbs up. Waaaay better than many other online data binding tutorials.

Day of Silence

2007-06-26T15:54:00.000-07:00

I sometimes listen to Pandora, a popular Internet radio site. Today, June 26, 2007, is the Day of Silence -- hence, no music streaming for the day. It's becuase "an arbitration committee in Washington DC has drastically increased the licensing fees Internet radio sites must pay to stream songs."

Pandora, along with a lot of other Internet radio sites are going off the air today.

There's something that music lovers (especially those who listen to internet music) can do. Call their Congressiona lrepresentatives and ask them to support the bill "Internet Radio Equality Act".

LearnWPF.com

2007-06-26T15:47:00.000-07:00

Just found out about LearnWPF.com today. It features some short WPF tutorials of some simple-and-common-yet-you-don't-know-how-to-do-it-right things. Some examples include data binding, creating image reflection (something like Apple's widgely used eye-candy visual effects), etc.

The correct way to repaint a form or control in c#

2007-06-15T23:59:00.000-07:00

There are two ways to repaint a form and its contents:

You can use one of the overloads of the Invalidate method with the Update method.
You can call the Refresh method, which forces the control to redraw itself and all its children. This is equivalent to setting the Invalidate method to true and using it with Update.

The Invalidate method governs what gets painted or repainted. The Update method governs when the painting or repainting occurs. If you use the Invalidate and Update methods together rather than calling Refresh, what gets repainted depends on which overload of Invalidate you use. The Update method just forces the control to be painted immediately, but the Invalidate method governs what gets painted when you call the Update method.

(Above info quoted from MSDN http://msdn2.microsoft.com/en-us/library/system.windows.forms.control.update.aspx)

Postable: convert codes to make them show up properly on a webpage

2007-06-12T00:55:00.000-07:00

http://www.elliotswan.com/postable/

Great free web-based tool by Elliot Swan that converts special HTML characters like < and > into &llt; and >