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Norman Ramsey

Norman Ramsey

Send email to nr@cs.tufts.edu.
Send physical documents to my postal address.
Telephone +1 781 393 4334.
Fax +1 814 253 0741
My vita and public key are online.
I was a charter member of the Triforce group.

I type 75 words per minute. Test yourself.

On this page:

Research

Recent developments in programming languages have broad implications for the safety and reliability of computer software as well as the productivity and competitiveness of the software industry. Trends in handheld devices like PDAs and cell phones suggest that future applications will demand sophisticated programming languages on diverse hardware platforms. In a world of rapidly changing languages and hardware, we cannot afford to spend years crafting a custom implementation of each language on each hardware platform. Instead, we must create implementation tools and techniques that can quickly and easily support new languages and new platforms. This is the goal of my research.

My current work focuses on compiler construction:

The ideal compiler infrastructure should support not only a variety of target machines but also a variety of programming languages. Past infrastructures have focused only on what happens at compile time. But to support such language features as garbage collection, exception dispatch, and concurrency, run-time support is needed. I have proposed providing such support not by upcalls but through a run-time interface, which reveals to the run-time system the important decisions made in the compiler's back end. This new organization should make compiler infrastructure significantly easier to reuse with multiple languages. This idea is being used in the C-- project.
Compiler writers have long used the idea of ``machine description'' to make a compiler easier to port to new machines. But a typical machine description actually describes an algorithm, not a machine, and does so in terms of a particular compiler's intermediate code—so it can't be reused. In the languages SLED and Lambda-RTL, I have pioneered declarative machine descriptions, which say only what the machine does and do so in terms that are independent of particular intermediate codes. Such descriptions are much easier to reuse, but the price you pay is that the description requires more thorough analysis to be useful in a compiler. My students and I are developing several analyses for this purpose.

In addition to compilers, I have also done work on interpreters, debuggers, other machine-level tools, language design, and formal methods. The full story can be found among my papers.

My research output often includes tools you can download and use.

Quick C-- includes a compiler and interpreter for C--. If you are interested in implementing a high-level language, try translating it to C-- and let us give you native code for several platforms.
Lua-ML is an implementation of the Lua scripting language in Objective Caml. It is useful for scripting and configuring Caml programs.
The New Jersey Machine-Code Toolkit implements SLED and is useful for building code that has to analyze or emit machine instructions: assemblers, disassemblers, binary translators, debuggers, and the like.
Noweb is a simple, extensible literate-programming tool. It supports any programming language and is widely used.

I have also written the ldb debugger and a translator for the Lambda-RTL machine-description language, but these tools are research prototypes and may not be useful right out of the box. Finally, NbibTeX has no research content, but it is a nice replacement for BibTeX.

I was a charter member of the Triforce group, which included Greg Morrisett, Mike Smith, and many others.

My research has been supported by an Alfred P. Sloan Research Fellowship, by grants from the National Science Foundation, from DARPA, and from the Australian Research Council, and by fellowships from the Fannie and John Hertz Foundation and from AT&T Bell Labs.

Selected papers

I have collected both highly significant and recent papers. Links are to abstracts so you can check out the topic without downloading a monster. For a complete view, including older work, see my publications list.

Five most significant papers

Relocating Machine Instructions by Currying. Proceedings of the ACM SIGPLAN '96 Conference on Programming Language Design and Implementation, in SIGPLAN Notices, 31(5):226–236, May 1996.
This paper connects two worlds: the ``low cult'' of systems programming and the pure, mathematical world of the lambda-calculus. The key insight is that relocation, which is a low-level operation performed on binary code, is an instance of currying, which is the expression of a multiple-argument function in the lambda-calculus.
A Single Intermediate Language That Supports Multiple Implementations of Exceptions (with Simon L. Peyton Jones). Proceedings of the ACM SIGPLAN '00 Conference on Programming Language Design and Implementation, in SIGPLAN Notices, 35(5):285–298, May 2000.
This paper is the most technical and rigorous of the C-- papers. It exemplifies what I am trying to achieve in C--: clean, low-level mechanisms that compiler writers can use to implement different high-level–language features and to control cost tradeoffs.
Stochastic Lambda Calculus and Monads of Probability Distributions (with Avi Pfeffer). Proceedings of the 29th ACM Symposium on the Principles of Programming Languages, in SIGPLAN Notices, 37(1):154–165, January 2002.
This paper explores the design of probabilistic languages in a foundational, principled way. Its special contribution is to analyze important implementation techniques in a way that is completely formal and is rigorously connected to the theory of probability.
A Transformational Approach to Binary Translation of Delayed Branches (with Cristina Cifuentes). ACM Transactions on Programming Languages and Systems, 25(2):210–224, March 2003.
The paper solves a small but difficult problem in analysis of binary codes. This problem is repeatedly a stumbling block for industry groups that work with binary codes, and I believe our solution is definitive.
An Expressive Language of Signatures (with Kathleen Fisher and Paul Govereau). In Proceedings of the Tenth ACM SIGPLAN International Conference on Functional Programming (ICFP'05), pages 27–40, September 2005.
In this paper, we identified an important class of programming problems the solutions to which cannot be expressed in current languages, and we showed that these problems can be solved by new mechanisms that cohere with an existing language.

Five other significant papers

Specifying Representations of Machine Instructions (with Mary F. Fernández). ACM Transactions on Programming Languages and Systems, 19(3):492–524, May 1997.
This is the most technical and the definitive description of my early work on declarative machine descriptions.
An Algebraic Approach to File Synchronization (with Elöd Csirmaz). In Proceedings of the 8th European Software Engineering Conference (ESEC) and 9th ACM SIGSOFT Symposium on the Foundations of Software Engineering (FSE-9), pages 175–185, September 2001.
This paper discusses how to maintain consistency among multiple replicas of files that may be modified concurrently. We proposed reasoning about this problem by examining the algebraic structure of a sequence of modifications.
A Generalized Algorithm for Graph-Coloring Register Allocation (with Michael D. Smith and Glenn Holloway). ACM SIGPLAN '04 Conference on Programming Language Design and Implementation, in SIGPLAN Notices, 39(6):277–288, June 2004.
A new technique for dealing with irregularities in target machines, which arise because not all machine registers can be used interchangeably. We hope this will be the definitive paper on handling irregular register files in a graph-coloring register allocator.
Staged Allocation: A Compositional Technique for Specifying and Implementing Procedure Calling Conventions (with Reuben Olinsky and Christian Lindig). In Proceedings of the 33rd ACM Symposium on the Principles of Programming Languages, pages 409–421, January 2006.
A specification language for parameter passing, unique in having a formal semantics. Together with an earlier paper on stack-frame layout, a complete approach to calling conventions.
Embedding an Interpreted Language Using Higher-Order Functions and Types. Journal of Functional Programming, 2008. To appear. (A previous version appeared in ACM SIGPLAN 2003 Workshop on Interpreters, Virtual Machines and Emulators.).
Homage to Olivier Danvy: How to embed an application-specific function into an interpreter simply by describing its type. The paper, while not technically deep, shows the capabilities of functional languages to elegant advantage, and it is representative of my work on interpreters.

Other recent papers

These are some recent papers not listed above. They are in chronological order, so the most recent work is at the bottom.

Widening Integer Arithmetic (with Kevin Redwine). In 13th International Conference on Compiler Construction (CC 2004), LNCS volume 2985, pages 232–249, April 2004.
A principled way to run 32-bit codes on a 64-bit machine. Shows which integer operators require sign extension, zero extension, or no extension. The most interesting contribution is not the algorithm itself, but a simple type system which classifies all arithmetic operations according to how they may be handled using a machine word that is too wide. The work generalizes to any pair of precisions.
Declarative Composition of Stack Frames (with Christian Lindig). In 13th International Conference on Compiler Construction (CC 2004), LNCS volume 2985, pages 298–312, April 2004.
A simple, powerful approach to stack-frame layout.
Source-level Debugging for Multiple Languages With Modest Programming Effort (with Sukyoung Ryu). In 14th International Conference on Compiler Construction (CC 2005), pages 10–26, April 2005.
How to add debugging support to a compiler while enabling the compiler to maintain natural representations of its source language, a natural ordering of its phases, and natural lifetimes of its internal data structures.
An Applicative Control-Flow Graph Based on Huet's Zipper (with João Dias). In ACM SIGPLAN Workshop on ML, pages 101–122, September 2005.
A control-flow graph for doing classical imperative-style optimization in your functional compiler.
ML Module Mania: A Type-Safe, Separately Compiled, Extensible Interpreter. In ACM SIGPLAN Workshop on ML, pages 172–202, September 2005.
A functional pearl that explains Lua-ML's extension mechanism: separately compiled libraries. For modules hackers everywhere.
Converting Intermediate Code to Assembly Code Using Declarative Machine Descriptions (with João Dias). In 15th International Conference on Compiler Construction (CC 2006), LNCS volume 3923, pages 217–231, March 2006.
A significant step toward our agenda of generating a compiler from declarative machine descriptions.
Teach Technical Writing in Two Hours per Week, October 2006. A handbook for teaching writing to students in science or engineering. Accompanied by a student's edition.
Automatically Generating Back Ends for a Portable Assembly Language Using Declarative Machine Descriptions (with João Dias). Technical report, Harvard University, January 2008.
This somewhat hasty technical report presents the most exciting results from João Dias's doctoral dissertation. Persons actually wishing to understand the results should ask Dias for a copy of the dissertation.

For a complete view, including older work, see my publications list.

The ACM requires this disclaimer:

The documents contained in these pages are included to ensure timely dissemination of scholarly and technical work on a non-commercial basis. Copyright and all rights therein are maintained by the authors or by other copyright holders, notwithstanding that they have offered their works here electronically. It is understood that all persons copying this information will adhere to the terms and constraints invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder.

Teaching

In 2007–2008 I am on unpaid leave.

In the past, I have taught CS 152 (Programming Languages), CS 251 (Advanced Systems Programming), CS 252r (Advanced Functional Programming), CS 253r (Compiler Support for Run-Time Services), and CS 257 (Programming with Concurrency).

Resources for Students

As I am on leave, I am not holding office hours or supervising new students.

I have gathered material of interest to research students, including resources for writers, how to give a talk, and how to get admitted to the Harvard PhD program.
Undergraduate research students might also be interested.

If you want details about our graduate programs you can consult both an overview and detailed requirements.

Other WWW Resources

I was program chair for ICFP '07.

After attending the Edinburgh Links meeting in 2005, I felt compelled to share my thoughts on the future of functional programming.

I no longer maintain a hot list; this is more of a random list. An interest in personal productivity and pointers from Benjamin Pierce and Phil Wadler got me to Inbox Zero on Wed 21 Feb 2007 at 6:00 PM. After serious lossage caused by various alarums and excursions, I recovered Zero at 6:30 PM on Mon 31 Dec 2007. It was a pleasure to start the New Year with an empty inbox!

I'm a Bellcore alumnus and a long-standing member of the Luxuriant Flowing Hair Club for Scientists, and I have an Erdös Number of 5. Despite these scientific credentials, I'm not ashamed to subscribe to a magazine with a centerfold.

Although it surprises some people, for over thirty years I have been a foot ball fan. When it's not football season, I've been known to play Guild Wars. I also have a rare autographed copy of Ad Verbum. In my copious free time, I enjoy overworking. I eat at the Harkness Cafeteria (where Anita used to make excellent vegetarian food) and at the Oxford Spa (where everyone makes excellent sandwiches). I try to avoid P. J. Brown's deadly sins. I'm married to a licensed psychologist.

We do not have a Department of Computer Science at Harvard. My professional home is in the Harvard School of Engineering and Applied Sciences.