<s>
Singularity	B-Language
is	O
a	O
free	B-License
and	O
open-source	B-Application
computer	I-Application
program	I-Application
that	O
performs	O
operating-system-level	B-Application
virtualization	I-Application
also	O
known	O
as	O
containerization	O
.	O
</s>
<s>
One	O
of	O
the	O
main	O
uses	O
of	O
Singularity	B-Language
is	O
to	O
bring	O
containers	B-Application
and	O
reproducibility	O
to	O
scientific	O
computing	O
and	O
the	O
high-performance	B-Architecture
computing	I-Architecture
(	O
HPC	O
)	O
world	O
.	O
</s>
<s>
The	O
need	O
for	O
reproducibility	O
requires	O
the	O
ability	O
to	O
use	O
containers	B-Application
to	O
move	O
applications	O
from	O
system	O
to	O
system	O
.	O
</s>
<s>
Using	O
Singularity	B-Language
containers	B-Application
,	O
developers	O
can	O
work	O
in	O
reproducible	O
environments	O
of	O
their	O
choosing	O
and	O
design	O
,	O
and	O
these	O
complete	O
environments	O
can	O
easily	O
be	O
copied	O
and	O
executed	O
on	O
other	O
platforms	O
.	O
</s>
<s>
In	O
2021	O
the	O
Singularity	B-Language
open	O
source	O
project	O
split	O
into	O
two	O
projects	O
called	O
Apptainer	B-Language
and	O
SingularityCE	B-Language
.	O
</s>
<s>
Singularity	B-Language
began	O
as	O
an	O
open-source	B-Application
project	I-Application
in	O
2015	O
,	O
when	O
a	O
team	O
of	O
researchers	O
at	O
Lawrence	O
Berkeley	O
National	O
Laboratory	O
,	O
led	O
by	O
Gregory	O
Kurtzer	O
,	O
developed	O
the	O
initial	O
version	O
written	O
in	O
the	O
C	B-Language
programming	I-Language
language	I-Language
and	O
released	O
it	O
under	O
the	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
By	O
the	O
end	O
of	O
2016	O
,	O
many	O
developers	O
from	O
different	O
research	O
facilities	O
joined	O
forces	O
with	O
the	O
team	O
at	O
Lawrence	O
Berkeley	O
National	O
Laboratory	O
to	O
further	O
the	O
development	O
of	O
Singularity	B-Language
.	O
</s>
<s>
Singularity	B-Language
quickly	O
attracted	O
the	O
attention	O
of	O
computing-heavy	O
scientific	O
institutions	O
worldwide	O
:	O
</s>
<s>
Various	O
sites	O
of	O
the	O
Open	O
Science	O
Grid	O
Consortium	O
including	O
Fermilab	O
started	O
adopting	O
Singularity	B-Language
;	O
by	O
April	O
2017	O
,	O
Singularity	B-Language
was	O
deployed	O
on	O
60%	O
of	O
the	O
Open	O
Science	O
Grid	O
network	O
.	O
</s>
<s>
For	O
two	O
years	O
in	O
a	O
row	O
,	O
in	O
2016	O
and	O
2017	O
,	O
Singularity	B-Language
was	O
recognized	O
by	O
HPCwire	O
editors	O
as	O
"	O
One	O
of	O
five	O
new	O
technologies	O
to	O
watch	O
"	O
.	O
</s>
<s>
In	O
2017	O
Singularity	B-Language
also	O
won	O
the	O
first	O
place	O
for	O
the	O
category	O
"	O
Best	O
HPC	O
Programming	O
Tool	O
or	O
Technology	O
"	O
.	O
</s>
<s>
based	O
on	O
the	O
data	O
entered	O
on	O
a	O
voluntary	O
basis	O
in	O
a	O
public	O
registry	O
,	O
Singularity	B-Language
user	B-Operating_System
base	I-Operating_System
was	O
estimated	O
to	O
be	O
greater	O
than	O
25,000	O
installations	O
and	O
included	O
users	O
at	O
academic	O
institutions	O
such	O
as	O
Ohio	O
State	O
University	O
and	O
Michigan	O
State	O
University	O
,	O
as	O
well	O
as	O
top	O
HPC	O
centers	O
like	O
Texas	O
Advanced	O
Computing	O
Center	O
,	O
San	O
Diego	O
Supercomputer	B-Architecture
Center	O
,	O
and	O
Oak	O
Ridge	O
National	O
Laboratory	O
.	O
</s>
<s>
In	O
February	O
2018	O
the	O
Sylabs	O
company	O
,	O
founded	O
by	O
the	O
Singularity	B-Language
author	O
,	O
was	O
announced	O
to	O
provide	O
commercial	O
support	O
for	O
Singularity	B-Language
.	O
</s>
<s>
In	O
October	O
of	O
that	O
year	O
Sylabs	O
released	O
version	O
3.0.0	O
which	O
was	O
a	O
rewrite	O
in	O
the	O
Go	B-Application
programming	I-Application
language	I-Application
.	O
</s>
<s>
In	O
May	O
2020	O
Gregory	O
Kurtzer	O
left	O
Sylabs	O
but	O
retained	O
leadership	O
of	O
the	O
Singularity	B-Language
open	O
source	O
project	O
.	O
</s>
<s>
In	O
May	O
2021	O
Sylabs	O
made	O
a	O
fork	B-Application
of	O
the	O
project	O
and	O
called	O
it	O
SingularityCE	B-Language
.	O
</s>
<s>
In	O
November	O
2021	O
the	O
Singularity	B-Language
open	O
source	O
project	O
joined	O
the	B-Operating_System
Linux	I-Operating_System
Foundation	I-Operating_System
and	O
was	O
renamed	O
to	O
Apptainer	B-Language
.	O
</s>
<s>
Singularity	B-Language
is	O
able	O
to	O
support	O
natively	O
high-performance	O
interconnects	O
,	O
such	O
as	O
InfiniBand	B-Architecture
and	O
Intel	O
Omni-Path	B-Operating_System
Architecture	I-Operating_System
(	O
OPA	O
)	O
.	O
</s>
<s>
Similar	O
to	O
the	O
support	O
for	O
InfiniBand	B-Architecture
and	O
Intel	O
OPA	O
devices	O
,	O
Singularity	B-Language
can	O
support	O
any	O
PCIe-attached	O
device	O
within	O
the	O
compute	O
node	O
,	O
such	O
as	O
graphic	B-Architecture
accelerators	I-Architecture
.	O
</s>
<s>
Singularity	B-Language
also	O
has	O
native	O
support	O
for	O
Open	B-Library
MPI	I-Library
library	O
by	O
utilizing	O
a	O
hybrid	O
MPI	O
container	B-Application
approach	O
where	O
OpenMPI	B-Library
exists	O
both	O
inside	O
and	O
outside	O
the	O
container	B-Application
.	O
</s>
<s>
These	O
features	O
make	O
Singularity	B-Language
increasingly	O
useful	O
in	O
areas	O
such	O
as	O
machine	O
learning	O
,	O
deep	B-Algorithm
learning	I-Algorithm
and	O
most	O
data-intensive	O
workloads	O
where	O
the	O
applications	O
benefit	O
from	O
the	O
high	O
bandwidth	O
and	O
low	O
latency	O
characteristics	O
of	O
these	O
technologies	O
.	O
</s>
<s>
HPC	B-Architecture
systems	I-Architecture
traditionally	O
already	O
have	O
resource	B-General_Concept
management	I-General_Concept
and	I-General_Concept
job	I-General_Concept
scheduling	I-General_Concept
systems	I-General_Concept
in	O
place	O
,	O
so	O
the	O
container	B-Application
runtime	O
environments	O
must	O
be	O
integrated	O
into	O
the	O
existing	O
system	O
resource	O
manager	O
.	O
</s>
<s>
Using	O
other	O
enterprise	O
container	B-Application
solutions	O
like	O
Docker	B-Language
in	O
HPC	B-Architecture
systems	I-Architecture
would	O
require	O
modifications	O
to	O
the	O
software	O
.	O
</s>
<s>
Docker	B-Language
containers	B-Application
can	O
be	O
automatically	O
converted	O
to	O
stand-alone	O
singularity	B-Language
files	O
which	O
can	O
then	O
be	O
submitted	O
to	O
HPC	O
resource	O
managers	O
.	O
</s>
<s>
Singularity	B-Language
seamlessly	O
integrates	O
with	O
many	O
resource	O
managers	O
including	O
:	O
</s>
