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The Denton Project began life with the aim of using Time-Warp
technology in object-oriented discrete event simulation...it turned
into a more general investigation into various aspects
of symbolic parallel processing. But we'll get back to simulation
real soon now.
Denton I, 1990-94
The first phase, in which we developed, implemented and experimented
with the design of
EuLisp, finished in 1994. The result was a system called
Feel which conforms to about 90% of the
EuLisp definition. Other developments have been a parallel
object-oriented reimplementation of OPS5, the porting and extension of
the Persistent Simulation Environment (originally developed at
Berkeley), integration of PVM to support
distributed processing, and remote control of a Maspar to support
data-parallel processing.
Denton II, 1994-date
The second phase started in October 1994, starting the construction of
a Virtual Multicomputer. This is an ephemeral,
geographically distributed, persistent multicomputer of available
heterogenous computing resources (workstation, shared-memory
multiprocessor, distributed memory multiprocessor, array processor).
The system supports a virtual processor abstraction to distribute data
and tasks across the multicomputer, the actual physical composition of
which may change dynamically.
We are using the following kit for our prototype system:
4 SGI Indys as workstations and
as "farm" components (some farm!)
A 5th SGI Indy is located at Southampton University, who are
collaborators in this project, where we also have access to an IBM
SP-2.
Our objective is to make it straightforward to prototype dynamic
distributed symbolic applications using whatever resources are
available (probably networked workstations), but so that the developed
program can also be run on more exotic hardware at a later stage. The
infrastructure for this is being developed in conjunction with David
DeRoure at the University of Southampton.
Applications are being developed in the framework of the VIM Project, in
particular, distributed agent-based systems, such as The Fishmarket
Project at IIIA (Bellaterra, nr Barcelona).
Since we are few people and our resources are limited, we have
concentrated our effort on the parts where we felt it was desireable
to build our own tools and re-used publicly available software for
everything else. Thus what exists of the virtual multicomputer so far
is
What makes Youtoo novel is that although code is compiled to bytecodes
and and the core of the runtime is a byte-coded virtual machine, in
order to support separate compilation, the byte codes are output as C
char* objects which can then be compiled with cc,
linked with ld and made into libraries with ar.
Naturally, this also means fast start-up and no need to load and
decode a preserved heap image, as well as making it easy to deliver
compiled Lisp applications.
Youtoo supports both in-calls and out-calls, the FFI being very
similar to that for Ilog Talk,
designed by Harley Davis et al. Although EuLisp has a simple thread
mechanism to support multi-threaded programming on any system, we have
also recently integrated both Solaris
Threads and Posix
Portable Common Runtime (PPCR) Threads.