1. Project Proposal Implementing library support for the Virgil programming language Ryan Hall Advisor: Jens Palsberg January 23, 2007

2. The Problem Sensor motes have very limited memory space on board (~few kb) Want to optimize memory space usage Want to ease this dilemma off the programmer Possible solution – place optimization in the programming language and compiler Why not wait for Moore’s Law?

3. Current Solution nesC C AVR Sensor Mote nesC compiler avr-gcc compiler Downloaded to mote - Language designed at UC Berkeley to embody structure of TinyOs - C programming language - Machine language that runs on motes

4. Problems with nesC Major Problem Lack of space optimization when nesC is compiled into C Minor Problems not an Object Oriented language not a type safe language

5. Proposed Solution Design a language and compiler that optimize memory usage on the motes Introduce object oriented principles into the language Classes, methods, delegates, etc… Introduce a strong type system Problems? Introduce all these abstractions, but still keep low- level interaction with hardware

6. Virgil Designed by Ben Titzer (grad student at UCLA) The Virgil compiler uses sophisticated memory optimization techniques Uses several OO principles from Java and C# to make programming easier and cleaner Strong type system to reduce common programming errors Runs without OS, scheduler or garbage collector – runs on bare hardware

7. nesC Revisited nesC C AVR Sensor Mote

8. Now With Virgil nesC C AVR Sensor Mote Virgil Memory Space Optimization!

9. Current State of Virgil Library support for the LEDs and timer of the motes has been written and tested on the AVRORA simulator Still need support for the other three peripherals (Serial Port, Sensor and Radio) Other language implementations still need to be completed

10. My Tasks on Virgil First test the current library support on the actual motes Become familiar with downloading code to the motes and running it Expect to complete in a week (might not be the first task though)

11. My Tasks on Virgil Next implement library support for the Serial Port, Sensor and Radio All of these are already implemented in nesC Plan to study these implementations and possibly reverse engineer those solutions Become familiar with Virgil – probably will begin writing simple programs like BLINK Spend a considerable time debugging the programs in AVRORA Hopefully run on applications on the motes

12. Future of Virgil The main goal behind Virgil is to make programming sensor networks easier and cleaner Must maintain a sense of modularity when writing the libraries Hopefully still maintain OO abstractions with the device drivers

13. Possible Problems It is uncertain whether the design features of Virgil will allow a simple interaction with the devices on the mote The language was designed before implementing any drivers Possibly could have overlooked key problems when making design decisions Only time will tell…

14. References http://compilers.cs.ucla.edu/virgil http://compilers.cs.ucla.edu/avrora

15. Questions?