<s>
In	O
computational	O
complexity	O
theory	O
,	O
the	O
parallel	B-Operating_System
computation	I-Operating_System
thesis	I-Operating_System
is	O
a	O
hypothesis	O
which	O
states	O
that	O
the	O
time	O
used	O
by	O
a	O
(	O
reasonable	O
)	O
parallel	O
machine	O
is	O
polynomially	O
related	O
to	O
the	O
space	O
used	O
by	O
a	O
sequential	O
machine	O
.	O
</s>
<s>
The	O
parallel	B-Operating_System
computation	I-Operating_System
thesis	I-Operating_System
was	O
set	O
forth	O
by	O
Chandra	O
and	O
Stockmeyer	O
in	O
1976	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
for	O
a	O
computational	B-Application
model	I-Application
which	O
allows	O
computations	O
to	O
branch	O
and	O
run	O
in	O
parallel	O
without	O
bound	O
,	O
a	O
formal	O
language	O
which	O
is	O
decidable	O
under	O
the	O
model	O
using	O
no	O
more	O
than	O
steps	O
for	O
inputs	O
of	O
length	O
n	O
is	O
decidable	O
by	O
a	O
non-branching	O
machine	O
using	O
no	O
more	O
than	O
units	O
of	O
storage	O
for	O
some	O
constant	O
k	O
.	O
Similarly	O
,	O
if	O
a	O
machine	O
in	O
the	O
unbranching	O
model	O
decides	O
a	O
language	O
using	O
no	O
more	O
than	O
storage	O
,	O
a	O
machine	O
in	O
the	O
parallel	O
model	O
can	O
decide	O
the	O
language	O
in	O
no	O
more	O
than	O
steps	O
for	O
some	O
constant	O
k	O
.	O
</s>
<s>
The	O
parallel	B-Operating_System
computation	I-Operating_System
thesis	I-Operating_System
is	O
not	O
a	O
rigorous	O
formal	O
statement	O
,	O
as	O
it	O
does	O
not	O
clearly	O
define	O
what	O
constitutes	O
an	O
acceptable	O
parallel	O
model	O
.	O
</s>
<s>
A	O
parallel	O
machine	O
must	O
be	O
sufficiently	O
powerful	O
to	O
emulate	O
the	O
sequential	O
machine	O
in	O
time	O
polynomially	O
related	O
to	O
the	O
sequential	O
space	O
;	O
compare	O
Turing	B-Architecture
machine	I-Architecture
,	O
non-deterministic	O
Turing	B-Architecture
machine	I-Architecture
,	O
and	O
alternating	B-Application
Turing	I-Application
machine	I-Application
.	O
</s>
<s>
Chandra	O
and	O
Stockmeyer	O
originally	O
formalized	O
and	O
proved	O
results	O
related	O
to	O
the	O
thesis	O
for	O
deterministic	O
and	O
alternating	B-Application
Turing	I-Application
machines	I-Application
,	O
which	O
is	O
where	O
the	O
thesis	O
originated	O
.	O
</s>
