Information Theory and Machine Learning

Research activity report, January-August 2000 - David MacKay

Error-correcting codes

The magnetic recording group at IBM Zurich research labs are still interacting with us, though the hoped-for support for one PhD student did not materialize. IBM have put a code designed by DJCM into a simulated hard drive and found a 1dB improvement over their state-of-the-art code. This corresponds to a 12% increase in stored data density.
DJCM continues work on generalizations of low-density parity-check codes and on codes robust to synchronization errors.
The collaboration with R.J.McEliece of Caltech has produced another paper on the theory of sparse graph codes.

Matthew Davey presented work from his PhD at the IEEE international symposium on Information Theory, and it will be published in the leading information theory journal, IEEE-IT.

Simon Wilson defended his thesis successfully in June.

Latent variable models

James Miskin is writing up his thesis on blind signal separation techniques, including applications to several data sets: blurred images; spectral image data from Hitachi; and DNA microarray data (in collaboration with researchers from the Department of Obstetrics and Gynaecology and the Department of Pathology).

Human-computer interfaces

David Ward has completed a first round of experiments on the Dasher interface, which combines an adaptive language model with a pointer to allow the user to write text efficiently using two-dimensional continuous gestures. Alan Blackwell, now a Lecturer in the Computer Laboratory, has helped us design experiments to quantify the useability of the interface. After one hour's use, typical users are able to write, with just one finger, at half their normal ten-finger typing speed. This work will be presented at a human-computer interaction conference this November.
David has also been developing improved language models that could be used both in Dasher and for text compression.

Teaching Physics

Sanjoy Mahajan continues to contribute to the assessment and improvement of departmental teaching. A survey of students from all four years suggested that many students pass through a Physics degree without improvement of their understanding of basic physical concepts such as Newton's first law.
Through the Royal Institution and the Gatsby Foundation, Sanjoy also developed and taught a mathematics and physics enrichment course for high school students in the Cambridge area.

Other topics

Andrew M. Childs and Ryan B. Patterson, two visiting undergraduates from Caltech, and DJCM have submitted a paper on `Exact sampling from non-attractive distributions using summary states'.

Plans for next year

Ed Ratzer (British) to start a PhD supported by a Mott studentship and a CASE award from Schlumberger Cambridge Research. Topic: Error-correcting codes.
Seb Wills (British) to start a PhD supported by an industrial CASE award from British Telecom. Topic: Inference and learning using simple hardware.
Felix Huerlimann (Swiss) to start a PhD supported by Microsoft Research Cambridge. Topic: Machine Learning.
John Barry (New Zealand) to start a PhD in January. [Funding details and topic to be determined.]
David MacKay <>
Last modified: Tue Aug 1 15:24:47 2000