<s>
BIGSIM	B-Operating_System
is	O
a	O
computer	O
simulation	O
and	O
performance	O
modeling	O
system	O
for	O
parallel	B-Operating_System
computing	I-Operating_System
,	O
typically	O
used	O
for	O
very	O
large	O
computer	B-Architecture
clusters	I-Architecture
.	O
</s>
<s>
BIGSIM	B-Operating_System
was	O
developed	O
at	O
the	O
University	O
of	O
Illinois	O
.	O
</s>
<s>
When	O
a	O
large	O
scale	O
,	O
often	O
supercomputer	B-Architecture
level	O
,	O
parallel	O
system	O
is	O
being	O
developed	O
,	O
it	O
is	O
essential	O
to	O
be	O
able	O
to	O
experiment	O
with	O
multiple	O
configurations	O
and	O
simulate	O
performance	O
.	O
</s>
<s>
BIGSIM	B-Operating_System
provides	O
these	O
facilities	O
by	O
allowing	O
the	O
simulation	O
of	O
performance	O
on	O
various	O
node	B-Architecture
topologies	I-Architecture
,	O
message	O
passing	O
and	O
scheduling	O
strategies	O
.	O
</s>
<s>
BIGSIM	B-Operating_System
includes	O
an	O
emulator	O
and	O
a	O
trace-based	B-Operating_System
simulator	I-Operating_System
.	O
</s>
<s>
The	O
simulator	O
is	O
a	O
discrete	O
event	O
simulator	O
(	O
based	O
on	O
the	O
POSE	O
system	O
)	O
which	O
is	O
trace	O
driven	O
and	O
uses	O
POSE	O
's	O
Charm++	B-Language
base	O
.	O
</s>
<s>
BIGSIM	B-Operating_System
can	O
simulate	O
both	O
the	O
processing	O
components	O
and	O
the	O
message	O
passing	O
system	O
to	O
provide	O
an	O
overall	O
view	O
of	O
system	O
performance	O
characteristics	O
.	O
</s>
