<s>
Parallel	B-Operating_System
Virtual	I-Operating_System
Machine	I-Operating_System
(	O
PVM	B-Operating_System
)	O
is	O
a	O
software	B-Application
tool	O
for	O
parallel	O
networking	O
of	O
computers	O
.	O
</s>
<s>
It	O
is	O
designed	O
to	O
allow	O
a	O
network	B-Architecture
of	O
heterogeneous	O
Unix	O
and/or	O
Windows	O
machines	O
to	O
be	O
used	O
as	O
a	O
single	O
distributed	O
parallel	B-Operating_System
processor	I-Operating_System
.	O
</s>
<s>
The	B-Application
software	I-Application
is	O
very	O
portable	O
;	O
the	O
source	O
code	O
,	O
available	O
free	O
through	O
netlib	B-Application
,	O
has	O
been	O
compiled	B-Language
on	O
everything	O
from	O
laptops	B-Device
to	O
Crays	O
.	O
</s>
<s>
PVM	B-Operating_System
enables	O
users	O
to	O
exploit	O
their	O
existing	O
computer	O
hardware	O
to	O
solve	O
much	O
larger	O
problems	O
at	O
less	O
additional	O
cost	O
.	O
</s>
<s>
PVM	B-Operating_System
has	O
been	O
used	O
as	O
an	O
educational	O
tool	O
to	O
teach	O
parallel	B-Operating_System
programming	I-Operating_System
but	O
has	O
also	O
been	O
used	O
to	O
solve	O
important	O
practical	O
problems	O
.	O
</s>
<s>
Version	O
3	O
was	O
released	O
in	O
March	O
1993	O
,	O
and	O
supported	O
fault	B-General_Concept
tolerance	I-General_Concept
and	O
better	O
portability	O
.	O
</s>
<s>
PVM	B-Operating_System
was	O
a	O
step	O
towards	O
modern	O
trends	O
in	O
distributed	B-Architecture
processing	I-Architecture
and	O
grid	B-Architecture
computing	I-Architecture
but	O
has	O
,	O
since	O
the	O
mid-1990s	O
,	O
largely	O
been	O
supplanted	O
by	O
the	O
much	O
more	O
successful	O
MPI	B-Application
standard	O
for	O
message	O
passing	O
on	O
parallel	B-Operating_System
machines	I-Operating_System
.	O
</s>
<s>
PVM	B-Operating_System
is	O
free	B-Application
software	I-Application
,	O
released	O
under	O
both	O
the	O
BSD	B-Operating_System
License	I-Operating_System
and	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
PVM	B-Operating_System
is	O
a	O
software	B-Application
system	O
that	O
enables	O
a	O
collection	O
of	O
heterogeneous	O
computers	O
to	O
be	O
used	O
as	O
a	O
coherent	O
and	O
flexible	O
concurrent	B-Operating_System
computational	O
resource	O
,	O
or	O
a	O
"	O
parallel	B-Operating_System
virtual	I-Operating_System
machine	I-Operating_System
"	O
.	O
</s>
<s>
The	O
individual	O
computers	O
may	O
be	O
shared-memory	O
or	O
local-memory	O
multiprocessors	B-Operating_System
,	O
vector	B-Operating_System
supercomputers	B-Architecture
,	O
specialized	O
graphics	B-Device
engines	I-Device
,	O
or	O
scalar	B-General_Concept
workstations	B-Device
and	O
PCs	B-Device
,	O
that	O
may	O
be	O
interconnected	O
by	O
a	O
variety	O
of	O
networks	O
,	O
such	O
as	O
Ethernet	O
or	O
FDDI	B-Protocol
.	O
</s>
<s>
PVM	B-Operating_System
consists	O
of	O
a	O
run-time	O
environment	O
and	O
library	O
for	O
message-passing	O
,	O
task	O
and	O
resource	O
management	O
,	O
and	O
fault	O
notification	O
.	O
</s>
<s>
While	O
PVM	B-Operating_System
will	O
not	O
automatically	O
make	O
a	O
commercial	O
software	B-Application
package	O
run	O
faster	O
,	O
it	O
does	O
provide	O
a	O
powerful	O
set	O
of	O
functions	O
for	O
manually	O
parallelizing	O
an	O
existing	O
source	O
program	O
,	O
or	O
for	O
writing	O
new	O
parallel/distributed	O
programs	O
.	O
</s>
<s>
The	O
PVM	B-Operating_System
software	B-Application
must	O
be	O
specifically	O
installed	O
on	O
every	O
machine	O
that	O
is	O
to	O
be	O
used	O
in	O
a	O
given	O
"	O
virtual	B-Architecture
machine	I-Architecture
"	O
.	O
</s>
<s>
There	O
is	O
no	O
"	O
automatic	O
"	O
installation	O
of	O
executables	B-Application
onto	O
remote	O
machines	O
in	O
PVM	B-Operating_System
,	O
although	O
simply	O
copying	O
the	O
pvm3/lib	O
and	O
pvm3/bin	O
directories	O
to	O
another	O
similar	O
machine	O
(	O
and	O
setting	O
$PVM_ROOT	O
and	O
$PVM_ARCH	O
)	O
is	O
sufficient	O
for	O
running	O
PVM	B-Operating_System
programs	O
.	O
</s>
<s>
Compiling	B-Language
or	O
building	O
PVM	B-Operating_System
programs	O
requires	O
the	O
full	O
PVM	B-Operating_System
installation	O
.	O
</s>
<s>
User	O
programs	O
written	O
in	O
C	B-Language
,	O
C++	B-Language
,	O
or	O
Fortran	B-Application
can	O
access	O
PVM	B-Operating_System
through	O
provided	O
library	O
routines	O
.	O
</s>
<s>
PVM	B-Operating_System
also	O
supports	O
broadcasting	B-Operating_System
(	O
PVM_bcast	O
)	O
which	O
sends	O
to	O
all	O
processes	O
in	O
a	O
group	O
and	O
multicasting	O
(	O
PVM_mcast	O
)	O
which	O
sends	O
to	O
a	O
specific	O
list	O
of	O
processes	O
.	O
</s>
