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Title: Spur, a new object representation for Cog
Speaker: Elliot Miranda
Wed, August 20, 9am – 10am
Part 1: https://www.youtube.com/watch?v=k0nBNS1aHZ4
Part 2: https://www.youtube.com/watch?v=sn3irBZE7g4
Part 3: https://www.youtube.com/watch?v=1Vg0iFeg_pA
Abstract: Spur is a new object representation and memory manager for the Cog VM. The object representation includes immediate characters and its simplicity allows Cog's JIT to implement many more operations, resulting in a faster VM. The object representation is designed to share the object header and the majority of the memory management code between 32-bit and 64-bit versions. Spur has two features new to Squeak/Pharo, the ability to grow and shrink memory via segments, and the ability to pin objects in memory. Spur has one altogether novel feature, a partial read barrier, which takes advantage of Smalltalk's message sending to provide lazy forwarding, which allows the system to implement become efficiently while retaining the speed advantages of direct pointers. This talk will explain these features with minimal manifestation of machine code on the slides and, for this author, plenty of pleasing pictures.
Bio: Eliot Miranda is a long-time Smalltalk systems programmer and virtual machine architect. He started his technical life developing holographic optics for bubble chamber physics, in so doing discovering a love of computing. His early work, started while a student at York University, produced the BrouHaHa series of virtual machines. These were Smalltalk-80 interpreters and threaded code JITs, written in C. While at Queen Mary College in the University of London he was involved in applying these implementations to prototyping what-you-see-is-what-i-see interfaces for IBM and to implementing the bulk of the software for the Active Book, a very early ARM-based tablet computer. He was virtual machine lead and then technical lead for VisualWorks for a decade at ParcPlace and its successors, before joining Cadence where he helped adapt Squeak to implement Newspeak. He then joined Qwaq, the company applying Croquet to business communications, where he implemented Cog. He is now back at Cadence in a team applying Cog and Newspeak to SoC design support. He is currently enjoying collaborating with a number of people on Cog-related projects, not least of which is an adaptive optimization system for Pharo/Squeak called Sista.