Call for attendees - Conference on Test Automation

Posted by Allen Hutchison, Engineering Manager

As we noted earlier, we're hosting our first-ever Conference on Test Automation in London in September.

We've heard from many interested parties, and now have 13 excellent presentations lined up. Now we are soliciting people who want to attend. Because we expect lots of interest and space is limited, we're asking everyone who's interested to write a short note (400 words or less) on why you want to be there. There's an easy form for requesting a spot, and we hope to hear from you. The deadline for writing in is July 28th - and you'll hear back by August 4.

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Interactive TV: Conference and Best Paper

Posted by Michele Covell & Shumeet Baluja, Research Scientists

Euro ITV (the interactive television conference) took place in Athens last week. The presentations included a diverse collection of user studies, new application areas, and exploratory business models. One of the main themes was the integration of multiple information sources. For example, during a time-out in a live sporting event, some viewers may enjoy reviewing highlight footage, while others may prefer to view a parallel program to view player profiles and statistics before being automatically returned to the soccer match once the event was back underway.

Other papers explored the idea of selecting and recommending videos. When many videos are available, such as through IPTV or digital cable, we see a heavy-tailed distribution of content accesses (much like that on the internet). There are a small number of popular channels but the combined viewings from thousands of "niche" channels outweigh the popular channels. As on the web, the problem that arises from this situation is one of discovery. A TV guide type resource is not practical; methods like collaborative-filtering can help. Nonetheless, new ideas and interfaces are needed.

We also presented our work at the conference. Our paper [pdf] (which received the best paper award :) focused on using broadcast viewing to automatically present relevant information on a web browser. We showed how to sample the ambient sound emitted from a TV and automatically determine what is being watched from a small signature of the sound -- all with complete privacy and minuscule effort. The system could keep up with users while they channel surf, presenting them with a real-time forum about a live political debate one minute and an ad-hoc chat room for a sporting event in the next. And, all of this would be done without users ever having to type or to even know the name of the program or channel being viewed. Taking this further, we could collect snippets from the web describing the actors appearing in a movie or present maps of locales within the movie as it takes place (no matter if users are watching it as a live broadcast or as a recoded broadcast).

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Extra, Extra - Read All About It: Nearly All Binary Searches and Mergesorts are Broken

Posted by Joshua Bloch, Software Engineer

I remember vividly Jon Bentley's first Algorithms lecture at CMU, where he asked all of us incoming Ph.D. students to write a binary search, and then dissected one of our implementations in front of the class. Of course it was broken, as were most of our implementations. This made a real impression on me, as did the treatment of this material in his wonderful Programming Pearls (Addison-Wesley, 1986; Second Edition, 2000). The key lesson was to carefully consider the invariants in your programs.

Fast forward to 2006. I was shocked to learn that the binary search program that Bentley proved correct and subsequently tested in Chapter 5 of Programming Pearls contains a bug. Once I tell you what it is, you will understand why it escaped detection for two decades. Lest you think I'm picking on Bentley, let me tell you how I discovered the bug: The version of binary search that I wrote for the JDK contained the same bug. It was reported to Sun recently when it broke someone's program, after lying in wait for nine years or so.

So what's the bug? Here's a standard binary search, in Java. (It's one that I wrote for the java.util.Arrays):

1:     public static int binarySearch(int[] a, int key) {
2:         int low = 0;
3:         int high = a.length - 1;
4:
5:         while (low <= high) {
6:             int mid = (low + high) / 2;
7:             int midVal = a[mid];
8:
9:             if (midVal < key)
10:                 low = mid + 1
11:             else if (midVal > key)
12:                 high = mid - 1;
13:             else
14:                 return mid; // key found
15:         }
16:         return -(low + 1);  // key not found.
17:     }

The bug is in this line:

 6:             int mid =(low + high) / 2;

In Programming Pearls Bentley says that the analogous line "sets m to the average of l and u, truncated down to the nearest integer." On the face of it, this assertion might appear correct, but it fails for large values of the int variables low and high. Specifically, it fails if the sum of low and high is greater than the maximum positive int value (2³¹ - 1). The sum overflows to a negative value, and the value stays negative when divided by two. In C this causes an array index out of bounds with unpredictable results. In Java, it throws ArrayIndexOutOfBoundsException.

This bug can manifest itself for arrays whose length (in elements) is 2³⁰ or greater (roughly a billion elements). This was inconceivable back in the '80s, when Programming Pearls was written, but it is common these days at Google and other places. In Programming Pearls, Bentley says "While the first binary search was published in 1946, the first binary search that works correctly for all values of n did not appear until 1962." The truth is, very few correct versions have ever been published, at least in mainstream programming languages.

So what's the best way to fix the bug? Here's one way:

 6:             int mid = low + ((high - low) / 2);

Probably faster, and arguably as clear is:

 6:             int mid = (low + high) >>> 1;

In C and C++ (where you don't have the >>> operator), you can do this:

 6:             mid = ((unsigned int)low + (unsigned int)high)) >> 1;

And now we know the binary search is bug-free, right? Well, we strongly suspect so, but we don't know. It is not sufficient merely to prove a program correct; you have to test it too. Moreover, to be really certain that a program is correct, you have to test it for all possible input values, but this is seldom feasible. With concurrent programs, it's even worse: You have to test for all internal states, which is, for all practical purposes, impossible.

The binary-search bug applies equally to mergesort, and to other divide-and-conquer algorithms. If you have any code that implements one of these algorithms, fix it now before it blows up. The general lesson that I take away from this bug is humility: It is hard to write even the smallest piece of code correctly, and our whole world runs on big, complex pieces of code.

We programmers need all the help we can get, and we should never assume otherwise. Careful design is great. Testing is great. Formal methods are great. Code reviews are great. Static analysis is great. But none of these things alone are sufficient to eliminate bugs: They will always be with us. A bug can exist for half a century despite our best efforts to exterminate it. We must program carefully, defensively, and remain ever vigilant.

Update 17 Feb 2008: Thanks to Antoine Trux, Principal Member of Engineering Staff at Nokia Research Center Finland for pointing out that the original proposed fix for C and C++ (Line 6), was not guaranteed to work by the relevant C99 standard (INTERNATIONAL STANDARD - ISO/IEC - 9899 - Second edition - 1999-12-01, 3.4.3.3), which says that if you add two signed quantities and get an overflow, the result is undefined. The older C Standard, C89/90, and the C++ Standard are both identical to C99 in this respect. Now that we've made this change, we know that the program is correct;)

Resources

• Programming Pearls - Highly recommended. Get a copy today!
• The Sun bug report describing this bug in the JDK
• A 2003 paper by Salvatore Ruggieri discussing a related problem - The problem is a bit more general but perhaps less interesting: the average of two numbers of arbitrary sign. The paper does not discuss performance, and its solution is not fast enough for use in the inner loop of a mergesort.

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Statistical machine translation live

Posted by Franz Och, Research Scientist

Because we want to provide everyone with access to all the world's information, including information written in every language, one of the exciting projects at Google Research is machine translation. Most state-of-the-art commercial machine translation systems in use today have been developed using a rules-based approach and require a lot of work by linguists to define vocabularies and grammars.

Several research systems, including ours, take a different approach: we feed the computer with billions of words of text, both monolingual text in the target language, and aligned text consisting of examples of human translations between the languages. We then apply statistical learning techniques to build a translation model. We have achieved very good results in research evaluations.

Now you can see the results for yourself. We recently launched an online version of our system for Arabic-English and English-Arabic. Try it out! Arabic is a very challenging language to translate to and from: it requires long-distance reordering of words and has a very rich morphology. Our system works better for some types of text (e.g. news) than for others (e.g. novels) -- and you probably should not try to translate poetry ... but do stay tuned for more exciting developments.

Update: We've just opened a discussion forum for all topics related to machine translation.

Update: Fixed broken link to NIST results.

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Our conference on automated testing

Posted by Allen Hutchison, Engineering Manager

Automated testing is one of my passions: it has hard problems to be solved, and they get harder every day. Over the past few years, I've had the opportunity to work on several automation projects, and now I'm getting a chance to combine my passion for automation with my love for the city of London.

I'm happy to announce that Google will be hosting a Conference on Test Automation in our London office on September 7 and 8, 2006. Our goal is to create a collegial atmosphere where participants can discuss challenges facing people on the cutting edge of test automation, and evaluate solutions for meeting those challenges.

Call for Presentations
We're looking for speakers with exciting ideas and new approaches to test automation. If you have a subject you'd like to talk about, please send me email at londontestconf@google.com that includes a description of your 60- or 90-minute talk in 500 words or less. Deadline for submissions is June 1.

We're planning to have 10 people give presentations at the conference followed by adequate time for discussion. If you'd like to attend as a non-speaker, watch this space. Once we've got a slate of speakers, we'll post it along with details on attending.

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See you at CHI

Posted by Rick Boardman, User Experience Researcher

The raison d’etre for our user experience research team is driven by Google's keen interest in focusing on the user. So we help many product teams provide the best possible experience to everyone around the world, primarily by inviting thousands of people to take part in usability tests in our labs, and by analyzing our logs to identify problems which need fixing. From this we get the data we help our engineers make Google products as easy as possible to use for the millions of people out there who think computers are far too complicated. People like my Mum, Dad, girlfriend, Gran — and pretty much everyone I know!

We’re one of several Google teams that publish research at academic and industry conferences, and this week a number of us will be attending the CHI (Computer-Human Interaction) conference in Montreal, the world's premiere gathering for CHI researchers and practitioners. Googlers from several teams will take part in eight sessions, each focusing on different aspects of human-computer interaction. (The full program is here – it’s a PDF file.)

A Large Scale Study of Wireless Search Behavior: Google Mobile Search – In a session on Search and Navigation: Mobiles and Audio, we'll present the first large-scale study of search behavior for mobile users, highlighting some shortcomings of wireless search interfaces.

Scaling the card sort method to over 500 items: Restructuring the Google AdWords Help Center – Here we adapt the popular card-sorting research methodology to large information sets where the traditional approach is impractical and discuss how we've applied this technique.

No IM Please, We’re Testing – During the Usability Evaluations: Challenges and Solutions session we’ll discuss the use of instant messaging tools like Google Talk in usability tests, and the benefits of this technique for enabling live collaboration between test moderators and observers.

Add a Dash of Interface: Taking Mash-Ups to the Next Level – Here we contribute to the discussion of how extendable interfaces like Google Maps are enabling exciting new online innovation through the combining of data sources.

Why Do Tagging Systems Work? – This panel will address the design challenges of scaling tagging systems to meet their recent surge in popularity. Gmail is an example of email tagging that offers more flexibility than traditional hierarchical systems.

Design Communication: How Do You Get Your Point Across? – A key challenge for UI designers is communicating solutions and challenges within product teams. This panel focuses on effective ways to do that.

“It’s About the Information, Stupid!” Why We Need a Separate Field of Human Information Interaction – This interdisciplinary panel will discuss arguments for and against a distinct field focusing on information rather than computing technology. One for the theoreticians? (-;

Incorporating Eyetracking into User Studies at Google – In this Eyetracking in Practice workshop, we’ll talk about some of the challenges we’ve encountered in studies of eyetracking in our labs.

If you work in, or study, the area of human-computer interaction, the user experience team is hiring. Right now we’re looking for user experience researchers (including those with specialized quantitative skills), UI designers, and more.

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First Robots

Posted by Sumit Agarwal, Maryam Kamvar, & Michael Stoppelman

With 4 seconds left to go, the Team Cheesy Poofs robot shouldered its way onto the 3 foot platform, pivoted 90 degrees into scoring position, and rapid-fired 10 balls directly into the 3-point goal. They won the match, and the Google Silicon Valley Regional Championship for US FIRST, a non-profit "For the Inspiration and Recognition of Science and Technology" (FIRST).

Google jumped at the opportunity to sponsor this organization after Dean Kamen (inventor of the Segway and the first implantable dialysis pump) spoke to a packed Google audience about his lifelong crusade to improve education in the United States. Dean founded US FIRST over 15 years ago, and from humble beginnings in the Northeast, FIRST has now grown to involve over 60,000 high school students all over the United States and the world.

FIRST was a natural partner for Google, given their focus on science and technology, their passion for changing the world for the better, and their single-minded focus on making education fun for students. When the final buzzer rang at the recent championship match the students jumped and hugged like they'd won the Superbowl. And in a way, they had. This event has all the excitement, tension, and drama of a major sporting event and then some.

Beyond sponsoring the FIRST tournament, Google also funded half a dozen teams in the Bay Area, ranging from East Palo Alto High School to Notre Dame High School. Several dozen employees also served as team mentors, meeting the students once a week to help construct the competition robots over the frantic six-week design/build cycle. Others volunteered at the Regional event as judges, coordinators, and referees, and plenty of Googlers were on hand to spectate the exciting matches.




We congratulate all the teams at the regional tournament for their hard work and innovation. We wish the six bay-area teams who qualified for the finals in Atlanta the best of luck . Bring home the gold!

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