<s>
LZFSE	B-Application
(	O
Lempel	O
–	O
Ziv	O
Finite	O
State	O
Entropy	O
)	O
is	O
an	O
open	B-Application
source	I-Application
lossless	B-Algorithm
data	I-Algorithm
compression	I-Algorithm
algorithm	O
created	O
by	O
Apple	O
Inc	O
.	O
</s>
<s>
It	O
was	O
released	O
with	O
a	O
simpler	O
algorithm	O
called	O
LZVN	B-Application
.	O
</s>
<s>
The	O
name	O
is	O
an	O
acronym	O
for	O
Lempel	O
–	O
Ziv	O
and	O
finite-state	O
entropy	O
(	O
implementation	O
of	O
asymmetric	B-General_Concept
numeral	I-General_Concept
systems	I-General_Concept
)	O
.	O
</s>
<s>
LZFSE	B-Application
was	O
introduced	O
by	O
Apple	O
at	O
its	O
Worldwide	O
Developer	O
Conference	O
2015	O
.	O
</s>
<s>
It	O
shipped	O
with	O
that	O
year	O
's	O
iOS	B-Operating_System
9	I-Operating_System
and	O
OS	B-Operating_System
X	I-Operating_System
10.11	I-Operating_System
releases	O
.	O
</s>
<s>
Apple	O
claims	O
that	O
LZFSE	B-Application
compresses	O
with	O
a	O
ratio	O
comparable	O
to	O
that	O
of	O
zlib	B-Language
(	O
DEFLATE	B-Algorithm
)	O
and	O
decompresses	O
two	O
to	O
three	O
times	O
faster	O
while	O
using	O
fewer	O
resources	O
,	O
therefore	O
offering	O
higher	O
energy	O
efficiency	O
than	O
zlib	B-Language
.	O
</s>
<s>
Part	O
of	O
this	O
energy	O
efficiency	O
was	O
achieved	O
by	O
optimising	O
the	O
algorithm	O
for	O
modern	O
micro-architectures	O
,	O
specifically	O
focusing	O
on	O
arm64	B-Architecture
.	O
</s>
<s>
Third-party	O
benchmarking	O
confirms	O
that	O
LZFSE	B-Application
decompresses	O
faster	O
than	O
zlib	B-Language
,	O
but	O
also	O
suggests	O
that	O
many	O
other	O
modern	O
compression	B-General_Concept
algorithms	I-General_Concept
may	O
have	O
more	O
favorable	O
compression	B-General_Concept
algorithm	I-General_Concept
performance	O
characteristics	O
such	O
as	O
density	O
,	O
compression	O
speed	O
and	O
decompression	O
speed	O
by	O
a	O
significant	O
margin	O
.	O
</s>
<s>
According	O
to	O
the	O
Squash	O
Benchmark	O
,	O
LZFSE	B-Application
is	O
similar	O
in	O
speed	O
to	O
ZSTD	B-Language
(	O
level	O
6	O
)	O
,	O
but	O
has	O
a	O
slightly	O
worse	O
ratio	O
.	O
</s>
<s>
LZVN	B-Application
is	O
similar	O
in	O
speed	O
to	O
LZ4	B-Language
level	O
4	O
,	O
with	O
a	O
slightly	O
worse	O
ratio	O
as	O
well	O
.	O
</s>
<s>
Neither	O
LZFSE	B-Application
nor	O
LZVN	B-Application
is	O
tunable	O
at	O
runtime	O
,	O
although	O
a	O
few	O
constants	O
can	O
be	O
tweaked	O
at	O
compile	O
time	O
for	O
the	O
usual	O
speed-ratio	O
trade-off	O
.	O
</s>
<s>
A	O
reference	O
C	B-Language
library	B-Library
written	O
by	O
Eric	O
Bainville	O
was	O
made	O
available	O
under	O
the	O
3-clause	O
BSD	B-Operating_System
License	I-Operating_System
after	O
WWDC	O
2016	O
.	O
</s>
<s>
It	O
includes	O
an	O
executable	O
to	O
compress	O
and	O
decompress	O
LZFSE	B-Application
streams	O
as	O
well	O
.	O
</s>
<s>
There	O
are	O
no	O
plans	O
to	O
expose	O
an	O
LZVN	B-Application
API	O
.	O
</s>
<s>
Apple	O
's	O
LZFSE	B-Application
implementation	O
uses	O
a	O
simpler	O
algorithm	O
called	O
LZVN	B-Application
when	O
the	O
input	O
is	O
smaller	O
than	O
(	O
4096	O
bytes	O
)	O
.	O
</s>
<s>
This	O
is	O
a	O
LZSS-type	B-Algorithm
algorithm	O
without	O
entropy	O
encoding	O
but	O
with	O
three	O
widths	O
of	O
REP	O
(	O
L	O
,	O
M	O
,	O
D	O
)	O
packets	O
.	O
</s>
<s>
In	O
the	O
open	B-Application
source	I-Application
reference	O
implementation	O
,	O
Apple	O
explains	O
that	O
LZFSE	B-Application
does	O
not	O
perform	O
as	O
well	O
for	O
small	O
sizes	O
,	O
so	O
LZVN	B-Application
is	O
used	O
instead	O
.	O
</s>
<s>
This	O
algorithm	O
in	O
libfastCompression.a	O
was	O
discovered	O
earlier	O
as	O
the	O
default	O
kernelcache	O
compression	O
method	O
in	O
Mac	B-Application
OS	I-Application
X	O
Yosemite	O
Developer	O
Preview	O
1	O
(	O
2014	O
)	O
,	O
replacing	O
the	O
legacy	O
compression	O
from	O
Haruhiko	O
Okumura	O
.	O
</s>
<s>
AppleFSCompression.framework	O
(	O
AFSC	O
)	O
,	O
the	O
mechanism	O
for	O
quasi-transparent	O
compression	O
in	O
HFS	B-Application
Plus	I-Application
and	O
Apple	B-Application
File	I-Application
System	I-Application
,	O
supports	O
LZFSE	B-Application
and	O
LZVN	B-Application
since	O
OS	O
X	O
10.9	O
.	O
</s>
<s>
Apple	O
's	O
Disk	B-Operating_System
Images	I-Operating_System
framework	O
has	O
offered	O
an	O
LZFSE-based	O
encoding	O
called	O
since	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
10.11	I-Operating_System
,	O
accessible	O
via	O
and	O
some	O
third-party	O
image	O
utilities	O
.	O
</s>
