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Java Massage Passing Interface
(JMPI)
A message passing interface for Java, called Java
Massage Passing Interface (JMPI), offers portability of to
applications and allows processes to communicate with each other by
passing messages. The JMPI was designed according to “Java
for MPI”, a standardized interface for message passing in
distributed Java applications that was defined by the Java Grande
Forum. Since MPI is the most popular programming model in cluster
computing, applications from computer clusters can be ported easily
to the system.
An example of a JMPI application is
given below. This application performs a parallel computation of an
integral and was executed on nodes of the P2P grid within our
research group.
1 import mpi.Comm;
2 import mpi.MPI;
3
4 public class Integral {
5 public migratory static double parIntegral (
double a, double b, long n ,int rank ,
int tasks ) throws javago.NotifyGone{
6 double result =
0.0
7 double h =(
b−a ) / n ;
8 long l ;
9 a = a+h/2 ;
10 for (l=rank;
l<n; l+=tasks) result += f (a+l*h) ;
11 return h*result;
12 }
13 public migratory static double f (double
x)throws javago.NotifyGone{
14 return (x*x) ;
15 }
16 public migratory static
void main ( String[] args ) throws javago.NotifyGone{
17 String address =
args[0];
18 try {
19 go(
" jgp://" + address + ":12000/" ) ;
20 }
21 catch (
Exceptione ) {
22 System.out.println("migration
failed") ;
23 }
24 Object buffer ;
25 int myrank,
nprocs, src;
26 double result,
x, T;
27 long n =1000000;
28 MPI.init( args, 1 );
29 nProcs = Comm.size( );
30 myRank = Comm.rank( );
31 result =
parIntegral(0.0, 1.0, n, myRank, nProcs) ;
32 if (myRank
>0){
33 buffer
= result;
34 Comm.send(buffer,
0, 1, MPI.DOUBLE, 0, 0) ;
35 else {
36 for(src=1;
src<nProcs; ++src ) {
37 x
=( Double ) Comm.recv(buffer, 0, 1, MPI.DOUBLE, src, 0) ;
38 result+=x;
39 }
40 }
41 MPI.finish();
42 }
43 }
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