One approach for building the next generation of parallel computers
is based on large aggregates of multiprocessor chips with support for
hardware multithreading. An initial design for IBM's Blue Gene/C
project exemplifies this approach. Such a machine might consist of a
million processors, and is characterized by a low memory-to-processor
ratio. To study alternate programming models for such a machine before
it is built, we have developed an emulator that allows
million-processor programs to be run on conventional parallel machines
with hundreds of processors. Here we present the implementation of a
parallel object model based on Charm++ as a candidate programming
model. Although the ``ideal'' programming model for such machines is a
matter of continuing research, we believe that parallel objects
represent a good starting point. This paper reviews the target
architecture, presents the programming model, and describes
the emulator implementation. Case studies of simple applications written
using the emulator are also discussed.
