<s>
Firefly	B-Application
,	O
formerly	O
named	O
PC	B-Application
GAMESS	I-Application
,	O
is	O
an	O
ab	O
initio	O
computational	O
chemistry	O
program	O
for	O
Intel-compatible	B-Operating_System
x86	B-Operating_System
,	O
x86-64	B-Device
processors	O
based	O
on	O
GAMESS	B-Application
(	O
US	O
)	O
sources	O
.	O
</s>
<s>
However	O
,	O
it	O
has	O
been	O
mostly	O
rewritten	O
(	O
60-70	O
%	O
of	O
the	O
code	O
)	O
,	O
especially	O
in	O
platform-specific	O
parts	O
(	O
memory	B-General_Concept
allocation	I-General_Concept
,	O
disk	O
input/output	B-General_Concept
,	O
network	B-Architecture
)	O
,	O
mathematic	O
functions	O
(	O
e.g.	O
,	O
matrix	B-Architecture
operations	O
)	O
,	O
and	O
quantum	O
chemistry	O
methods	O
(	O
such	O
as	O
Hartree	O
–	O
Fock	O
method	O
,	O
Møller	O
–	O
Plesset	O
perturbation	O
theory	O
,	O
and	O
density	O
functional	O
theory	O
)	O
.	O
</s>
<s>
Thus	O
,	O
it	O
is	O
significantly	O
faster	O
than	O
the	O
original	O
GAMESS	B-Application
.	O
</s>
<s>
Since	O
October	O
2008	O
,	O
the	O
project	O
is	O
no	O
longer	O
associated	O
with	O
GAMESS	B-Application
(	O
US	O
)	O
and	O
the	O
Firefly	B-Application
rename	O
occurred	O
.	O
</s>
<s>
Until	O
October	O
17	O
,	O
2009	O
,	O
both	O
names	O
could	O
be	O
used	O
,	O
but	O
thereafter	O
,	O
the	O
package	O
should	O
be	O
referred	O
to	O
as	O
Firefly	B-Application
exclusively	O
.	O
</s>
<s>
On	O
December	O
4	O
,	O
2009	O
,	O
the	O
support	O
of	O
any	O
PC	B-Application
GAMESS	I-Application
versions	O
earlier	O
than	O
the	O
first	O
PC	B-Application
GAMESS	I-Application
Firefly	B-Application
version	O
7.1.C	O
was	O
abandoned	O
,	O
and	O
any	O
and	O
all	O
licenses	O
to	O
use	O
the	O
code	O
were	O
revoked	O
.	O
</s>
<s>
Thus	O
,	O
users	O
of	O
the	O
outdated	O
PC	B-Application
GAMESS	I-Application
binaries	O
(	O
version	O
7.1.B	O
and	O
all	O
earlier	O
releases	O
)	O
were	O
required	O
to	O
discontinue	O
using	O
the	O
PC	B-Application
GAMESS	I-Application
and	O
upgrade	O
to	O
Firefly	B-Application
.	O
</s>
<s>
On	O
July	O
25	O
,	O
2012	O
,	O
a	O
state	O
of	O
the	O
art	O
edition	O
of	O
Firefly	B-Application
,	O
version	O
8.0.0	O
RC	O
,	O
was	O
launched	O
for	O
public	O
beta	O
testing	O
.	O
</s>
<s>
A	O
relative	O
comparison	O
has	O
shown	O
that	O
it	O
is	O
far	O
faster	O
and	O
more	O
reliable	O
than	O
the	O
prior	O
edition	O
,	O
Firefly	B-Application
7.1.G	O
.	O
</s>
<s>
In	O
the	O
Quantum	O
Chemistry	O
Speed	O
Test	O
,	O
Firefly	B-Application
's	O
DFT	O
code	O
came	O
second	O
(	O
losing	O
only	O
to	O
commercial	O
QChem	O
)	O
,	O
beating	O
other	O
free	O
DFT	O
codes	O
by	O
a	O
large	O
margin	O
.	O
</s>
<s>
Firefly	B-Application
's	O
unique	O
capabilities	O
include	O
XMCQDPT2	O
,	O
a	O
reformulation	O
of	O
Nakano	O
's	O
multi-state	O
multi-configuration	O
quasi-degenerate	O
perturbation	O
theory	O
(	O
MCQDPT	O
)	O
correcting	O
for	O
some	O
of	O
its	O
deficiencies	O
.	O
</s>
<s>
At	O
the	O
end	O
of	O
2019	O
,	O
Firefly	B-Application
's	O
main	O
developer	O
A	O
.	O
</s>
