1. Process Mobility on the JVM for ProcessJ
CPA 2009

2. Intro to ProcessJ ProcessJ is a new process-oriented language
Syntax close to Java and a semantics close to occam-π
Scoping rules similar to Java
Provides an approachable environment for broader audience of imperative programmers
Multiple target platforms

3. Intro to ProcessJ Multiplexer Example (Occam)
PROC mux (CHAN INT in1?, in2?, out!)
  INT data:
WHILE TRUE
ALT
    in1 ? data
out ! data
in2 ? data

4. Intro to ProcessJ Multiplexer Example
proc void mux(chan<int>.read in1,
              chan<int>.read in2,
              chan<int>.write out) {
    int data;
    while (true) {
        alt {
            data = in1.read() :
                out.write(data);
            data = in2.read() :
        }
    } }

5. Intro to ProcessJ Sequential subset mimics Java/C
Sequential subset mimics Java/C
Semicolon delimited statements
Assignment, arithmetic
Conditionals
For, While loops

6. Intro to ProcessJ
Channels look like objects with read, write methods (as in JCSP)
Special syntax for:
Par blocks
Alt bocks
Parallel For loops

7. Our Compiler Multiple backends MPI, Java (JCSP), Occam
Java backend targets Java source code
Take advantage of javac's optimizer

8. JCSP / JCSP.net Serialization Network Classloading
Mobile Channels, Processes

9. Process Mobility Illustrate process mobility in JCSP
Peter Welch - Bond example (jcsp.net pg 88)

10. Process Mobility Certain behavior implied at suspend point
mobile proc void foo() {
    int a = 0;
    while (a == 0) {
        a = a + 1;
        suspend;
        a = a - 1;
    } }

11. Challenges of the platform
No continuations
Limitations on flow control

12. Suspending
Support must be added for saving and restoring the local variable part of the JVM activation record -
Return control to caller

13. Resuming Restore activation record
Jump to appropriate bytecode instruction
Goto would be nice!

14. Code Outline public class Foo { private Object[] actRec;
private int jumpTarget
public void foo() {
...
switch (jumpTarget) {
case 1: goto #1;
default: break; }
while(1) {
suspend();
; #1
} } }

15. Source Code Rewriting Methods
Must separate code into regions between suspend calls (Fuenfrocken 98)
Java compiler sensitive to visibility of declared variables
Large overhead in generated LOCs

16. Bytecode Transformation
-Truyen
-Bouchenak

17. Overview of transformation

18. Bytecode Transformation