<s>
and	O
MATLAB	B-Language
to	O
provide	O
this	O
functionality	O
.	O
</s>
<s>
A	O
powerful	O
matrix-free	O
feature	O
of	O
ARPACK	B-Application
is	O
its	O
ability	O
to	O
use	O
any	O
matrix	O
storage	O
format	O
.	O
</s>
<s>
This	O
is	O
possible	O
because	O
it	O
does	O
n't	O
operate	O
on	O
the	O
matrices	B-Architecture
directly	O
,	O
but	O
instead	O
when	O
a	O
matrix	O
operation	O
is	O
required	O
it	O
returns	O
control	O
to	O
the	O
calling	O
program	O
with	O
a	O
flag	O
indicating	O
what	O
operation	O
is	O
required	O
.	O
</s>
<s>
The	O
calling	O
program	O
must	O
then	O
perform	O
the	O
operation	O
and	O
call	O
the	O
ARPACK	B-Application
routine	O
again	O
to	O
continue	O
.	O
</s>
<s>
Due	O
to	O
stalled	O
upstream	O
development	O
,	O
ARPAСK	O
has	O
been	O
forked	O
into	O
ARPACK-NG	O
,	O
as	O
a	O
form	O
of	O
a	O
collaborative	O
effort	O
of	O
the	O
various	O
groups	O
that	O
rely	O
on	O
ARPACK	B-Application
.	O
</s>
