Robert O'Callahan

After seven years, I finally graduated from the CMU School of Computer Science. My advisors were Daniel Jackson and Jeannette Wing. At CMU, I investigated the construction of automatic tools to help people build better software. On November 20, 2000, I successfully defended my thesis on Generalized Aliasing as a Basis for Program Analysis Tools.

I have accepted a position at the IBM Watson Research Center.

Travel: I will be on the US west coast from May 31 to June 13. Email contact will be intermittent during that time.

Personal Information

I'm married to Weiyee (Janet) Chui.

Before my studies at CMU, I was an undergraduate at the University of Auckland Computer Science Department, in New Zealand. A lot of people say that New Zealand is the most beautiful country in the world --- they're right!

I'm a Christian. I have been served with the local Asian Christian Fellowship and the Pittsburgh Chinese Church.

Check out my online photo album!

Research

I am interested in many areas of computer science, but one question occupies me more than any other: How can we make it easier for everyone to produce better software? My approach is to investigate the use of automatic tools to assist programmers in writing, understanding, testing and debugging code, by building tools and evaluating them in the context of real programs.

• For my thesis, I built Ajax, a system for discovering properties of Java programs using static analysis of their Java bytecode. Ajax adapts polymorphic type inference, similar to that used in ML, to produce generalized aliasing information. The aliasing information is fed into various tools, each tool customized to help with a particular programming task. Ajax can analyze large Java applications such as Sun's javac compiler and the javafig drawing package.
• Prior to my thesis, I built Lackwit, a tool for analyzing C code, which used a similar analysis engine to Ajax but lacked Ajax's customizability. Lackit was the first system to perform context-sensitive alias analysis of a program with more than 100,000 lines of code (a Linux 2.0 kernel). This work was published in ICSE '97.
• I've applied some of my ideas about bytecode analysis to the problem of bytecode verification. My paper about a very simple and powerful type system for verifying bytecode subroutines appeared in POPL '99. It can be read as an argument for using TAL/STAL-like type systems (based on classical type-theoretic ideas such as continuations and polymorphic recursion) to typecheck low-level languages, instead of the "dataflow analysis" style typechecking performed by the JVM.
• I spent two summers working on projects related to dynamic program analysis. At IBM Watson, I built a binary instrumentation tool to compute the dynamic data-flow graphs of C++ programs. These graphs show that a large percentage of the results computed by a typical application during its execution are never used. At DEC (now Compaq) SRC, I built a graphical user interface to their Digital Continuous Profiling Infrastructure tool. It was challenging to build an interface to quickly and inuitively navigate through the voluminous and detailed data gathered by DCPI.

I think one of my strengths is the ability to produce a lot of ideas. Of course they're not all good ideas :-).

Other Activities

I have plenty of other things to do when I'm not working on my research. Many of them are computer-related. Some are important, some are just for fun, some are both, but all are to the glory of God.

• I wrote TTSSH, a free SSH client for Windows (95 and NT), based on Teraterm Pro. There are hundreds of thousands of people using TTSSH. The TTSSH source code is available under the BSD license.
• I have built a very simple, very fast, index-based search engine that can search for arbitrary substrings in binary data. I have integrated this engine into the Cyrus IMAP server, so that searches over the bodies of tens of thousands of messages take place almost instantly. The source code for this should be available soon.
• Other hacks:
  • I wrote NT FingerService, a full-featured finger daemon for Windows NT. Its source code is also available.
  • Ever noticed how useful it is to be able to hear your disk working? Try PerfNoise, a cute hack for NT (with source) that lets you hear your CPU chugging away!
  • The Random Art Screensaver for Windows NT and Windows 95. Random Art algorithm courtesy of Andrej Bauer.
  • The Takapuna Screensaver for Windows NT and Windows 95.
  • I have some Java applets. They include a "shared virtual card table" that is rather different in philosophy and execution to all the other network play environments I've seen, even up till today. (It was written in 1996.) The source is available.
• I contributed some code to Mozilla, including its implementation of justified text. I am a super-reviewer and "driver" for the project (when time permits!).
• CMU users only: check out Harry Bovik's registration list.
• I spend a lot of time in various roles with the Asian Christian Fellowship.
• I enjoy games very much. I especially enjoy simple strategy games with a social element, such as mahjong and card games.
• Janet and I go to ballroom dancing classes regularly. I'm a terrible dancer but we enjoy it. I think it's a good idea to sometimes do things that I'm bad at --- that's why I go ice-skating, too.
• I'm terrible at sports, but I like the outdoors. I like to walk fast and far. I also like to swim, but only in the ocean.

Résumé

My résumé is on-line. I also have statements about my research and teaching.

Contact Information

For secure communication, you can use PGP:

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