<s>
Eigen	B-Language
is	O
a	O
high-level	O
C++	B-Language
library	B-Library
of	O
template	B-Application
headers	I-Application
for	O
linear	B-Language
algebra	I-Language
,	O
matrix	B-Architecture
and	O
vector	O
operations	O
,	O
geometrical	O
transformations	O
,	O
numerical	B-General_Concept
solvers	I-General_Concept
and	O
related	O
algorithms	O
.	O
</s>
<s>
Eigen	B-Language
is	O
open-source	B-Application
software	I-Application
licensed	O
under	O
the	O
Mozilla	B-License
Public	I-License
License	I-License
2.0	I-License
since	O
version	O
3.1.1	O
.	O
</s>
<s>
Earlier	O
versions	O
were	O
licensed	O
under	O
the	O
GNU	B-Application
Lesser	I-Application
General	I-Application
Public	I-Application
License	I-Application
.	O
</s>
<s>
Eigen	B-Language
is	O
implemented	O
using	O
the	O
expression	B-Application
templates	I-Application
metaprogramming	B-Language
technique	O
,	O
meaning	O
it	O
builds	O
expression	O
trees	O
at	O
compile	O
time	O
and	O
generates	O
custom	O
code	O
to	O
evaluate	O
these	O
.	O
</s>
<s>
Using	O
expression	B-Application
templates	I-Application
and	O
a	O
cost	O
model	O
of	O
floating	B-Algorithm
point	I-Algorithm
operations	O
,	O
the	O
library	B-Library
performs	O
its	O
own	O
loop	B-Operating_System
unrolling	I-Operating_System
and	O
vectorization	B-General_Concept
.	O
</s>
<s>
Eigen	B-Language
itself	O
can	O
provide	O
BLAS	B-Application
and	O
a	O
subset	O
of	O
LAPACK	B-Application
interfaces	O
.	O
</s>
