Hi,
I have built openmpi-1.9a1r27380 with Java support and try some small
programs. When I try to scatter an object, I get a ClassCastException.
I use the following object.
public class MyData implements java.io.Serializable
{
static final long serialVersionUID = -5243516570672186644L;
private int age;
private String name;
private double salary;
public MyData ()
{
age = 0;
name = "";
salary = 0.0;
}
public void setAge (int newAge)
{
age = newAge;
}
...
}
I use the following main program.
import mpi.*;
public class ObjectScatterMain
{
public static void main (String args[]) throws MPIException
{
int mytid; /* my task id */
MyData dataItem, objBuffer;
String processor_name; /* name of local machine */
MPI.Init (args);
processor_name = MPI.Get_processor_name ();
mytid = MPI.COMM_WORLD.Rank ();
dataItem = new MyData ();
objBuffer = new MyData ();
if (mytid == 0)
{
/* initialize data item */
dataItem.setAge (35);
dataItem.setName ("Smith");
dataItem.setSalary (2545.75);
}
MPI.COMM_WORLD.Scatter (dataItem, 0, 1, MPI.OBJECT,
objBuffer, 0, 1, MPI.OBJECT, 0);
/* Each process prints its received data item. The outputs
* can intermingle on the screen so that you must use
* "-output-filename" in Open MPI.
*/
System.out.printf ("\nProcess %d running on %s.\n" +
" Age: %d\n" +
" Name: %s\n" +
" Salary: %10.2f\n",
mytid, processor_name,
objBuffer.getAge (),
objBuffer.getName (),
objBuffer.getSalary ());
MPI.Finalize();
}
}
I get the following error, when I compile and run the program.
tyr java 218 mpijavac ObjectScatterMain.java
tyr java 219 mpiexec java ObjectScatterMain
Exception in thread "main" java.lang.ClassCastException:
MyData cannot be cast to [Ljava.lang.Object;
at mpi.Intracomm.copyBuffer(Intracomm.java:119)
at mpi.Intracomm.Scatter(Intracomm.java:389)
at ObjectScatterMain.main(ObjectScatterMain.java:45)
--------------------------------------------------------------------------
mpiexec has exited due to process rank 0 with PID 25898 on
...
Has anybody an idea why I get a ClassCastException or how I must define
an object, which I can use in a scatter operation? Thank you very much
for any help in advance.
Kind regards
Siegmar
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