<s>
Parallel	B-Operating_System
slowdown	I-Operating_System
is	O
a	O
phenomenon	O
in	O
parallel	B-Operating_System
computing	I-Operating_System
where	O
parallelization	B-Operating_System
of	O
a	O
parallel	B-Operating_System
algorithm	I-Operating_System
beyond	O
a	O
certain	O
point	O
causes	O
the	O
program	O
to	O
run	O
slower	O
(	O
take	O
more	O
time	O
to	O
run	O
to	O
completion	O
)	O
.	O
</s>
<s>
Parallel	B-Operating_System
slowdown	I-Operating_System
is	O
typically	O
the	O
result	O
of	O
a	O
communications	O
bottleneck	O
.	O
</s>
<s>
At	O
some	O
point	O
,	O
the	O
communications	O
overhead	O
created	O
by	O
adding	O
another	O
processing	O
node	O
surpasses	O
the	O
increased	O
processing	O
power	O
that	O
node	O
provides	O
,	O
and	O
parallel	B-Operating_System
slowdown	I-Operating_System
occurs	O
.	O
</s>
<s>
Parallel	B-Operating_System
slowdown	I-Operating_System
occurs	O
when	O
the	O
algorithm	O
requires	O
significant	O
communication	O
,	O
particularly	O
of	O
intermediate	O
results	O
.	O
</s>
<s>
Some	O
problems	O
,	O
known	O
as	O
embarrassingly	B-Operating_System
parallel	I-Operating_System
problems	I-Operating_System
,	O
do	O
not	O
require	O
such	O
communication	O
,	O
and	O
thus	O
are	O
not	O
affected	O
by	O
slowdown	O
.	O
</s>
