JavaParty

Object Location

An object layout with good locality is critical for a JavaParty application to achieve good performance. The initial location of a remote object allocated with the new statement is determined in one of the following ways:

1. If the programmer does not care about object placement, it is determined by a distributor class that may be specified when executing the JavaParty application. For detailed information about the distributor objects please refer to the JavaParty API documentation.

   Because the concept of object and class distributors does not require the mixing of application code with distribution code, this approach is very attractive. The application continues to look like regular non-distributed Java and the allocation decisions are made transparent to the application code by the runtime system. Unfortunately, the information that can be passed to the distributor object only consists of the name of the class that is instantiated and may not suffice to make a well-informed decision.

2. The object layout can also be specified directly at the statement where the allocation occurs. JavaPary uses a program annotation in form of a Java documentation comment specifying the node of the object to be allocated with the tag @at.

   The following code snippet allocates an object of remote class R on each node of the distributed environment.

   import jp.lang.DistributedRuntime;
   
   public void foo() {
      int cnt = DistributedRuntime.getMachineCnt();
      for (int n = 0; n < cnt; n++) {
         /** @at n */
         R r = new R();
      }
   }
   

Since good object locality is important, please also read the sections about Object migration and Remote Threads.