"ROSS: A High-Performance, Low Memory, Modular Time Warp System"
C. D Carothers, D. Bauer and S. Pearce
Journal of Parallel and Distributed Computing (JPDC) #62, pages 1648-1669, 2002
ABSTRACT
In this paper, we introduce a new Time Warp system called {\em ROSS:
Rensselaer's Optimistic Simulation System}. ROSS is an extremely
modular kernel that is capable of achieving event rates as high as
1,250,000 events per second when simulating a wireless telephone
network model (PCS) on a quad processor PC server. In a head-to-head
comparison, we observe that ROSS out performs the Georgia Tech Time
Warp (GTW) system by up to 180\% on a quad processor PC server and up
to 200\% on the SGI Origin 2000 . ROSS only requires a small {\em
constant} amount of memory buffers greater than the amount needed by
the sequential simulation for a constant number of processors. ROSS
demonstrates for the first time that stable, highly-efficient
execution using little memory above what the sequential model would
require is possible for low-event granularity simulation models. The
driving force behind these high-performance and low memory utilization
results is the coupling of an efficient pointer-based implementation
framework, Fujimoto's fast GVT algorithm for shared memory
multiprocessors, {\em reverse computation} and the introduction of
{\em Kernel Processes (KPs)}. KPs lower fossil collection overheads
by aggregating processed event lists. This aspect allows fossil
collection to be done with greater frequency, thus lowering the
overall memory necessary to sustain stable, efficient parallel
execution. These characteristics make ROSS an ideal system for use in
large-scale networking simulation models. The principle conclusion
drawn from this study is that the performance of an optimistic
simulator is largely determined by its memory usage.