CSP for Java
(JCSP) 1.1-rc4

Class MergeInt

  extended by org.jcsp.plugNplay.ints.MergeInt
All Implemented Interfaces:

public final class MergeInt
extends Object
implements CSProcess

Merges an array of strictly increasing int input streams into one strictly increasing output stream.

Process Diagram


MergeInt is a process whose output stream is the ordered merging of the integers on its input streams. It assumes that each input stream is strictly increasing (i.e. with no repeats) sequence of integers. It generates a strictly increasing output stream containing all -- and only -- the numbers from its input streams (eliminating any duplicates).

Warning: this process assumes that its input channel array has at least two elements.

Channel Protocols

Input Channels
in[] int Assume: in.length >= 2.
Output Channels
out int All channels in this package carry integers.


The following example shows how to use MergeInt in a small program. The program also uses some of the other plugNplay processes. The program prints, in ascending order (up to Integer.MAX_VALUE), all integers whose prime factors consist only of 2, 3, 5 and 7. Curious readers may like to reason why the infinitely buffered channels are needed.
 import org.jcsp.lang.*;
 import org.jcsp.util.ints.*;
 import org.jcsp.plugNplay.ints.*;
 public class MergeIntExample {
   public static void main (String[] argv) {
     final One2OneChannelInt[] a = Channel.one2oneIntArray (5);
     final One2OneChannelInt[] b = Channel.one2oneIntArray (4, new InfiniteBufferInt ());
     final One2OneChannelInt c = Channel.one2oneInt ();
     final One2OneChannelInt d = Channel.one2oneInt ();
     new Parallel (
       new CSProcess[] {
         new MultInt (2, a[0].in (), b[0].out ()),
         new MultInt (3, a[1].in (), b[1].out ()),
         new MultInt (5, a[2].in (), b[2].out ()),
         new MultInt (7, a[3].in (), b[3].out ()),
         new MergeInt (Channel.getInputArray (b), c.out ()),
         new PrefixInt (1, c.in (), d.out ()),
         new DeltaInt (d.in (), Channel.getOutputArray (a)),
         new PrinterInt (a[4].in (), "--> ", "\n")
     ).run ();

Implementation Note

The implementation sets up a balanced binary tree of parallel Merge2Int processes to fan-in the merge from its external input channels to its external output. It's a nice example of recursion and parallelism -- here's the run method:
   public void run () {
     final int n = in.length;  // deduce: n >= 2
     switch (n) {
       case 2:
         new Merge2Int (in[0], in[1], out).run ();
       case 3:
         final One2OneChannelInt c = Channel.one2oneInt ();
         new Parallel (
           new CSProcess[] {
             new Merge2Int (in[0], in[1], c.out ()),
             new Merge2Int (c.in (), in[2], out)
         ).run ();
       default:  // deduce: n >= 4
         final int n2 = n/2;
         ChannelInputInt[] bottom = new ChannelInputInt[n2];
         ChannelInputInt[] top = new ChannelInputInt[n - n2];
         for (int i = 0; i < n2; i++) {
           bottom[i] = in[i];
         for (int i = n2; i < n; i++) {
           top[i - n2] = in[i];
         final One2OneChannelInt[] d = Channel.one2oneIntArray (2);
         new Parallel (
           new CSProcess[] {
             new MergeInt (bottom, d[0].out ()),
             new MergeInt (top, d[1].out ()),
             new Merge2Int (d[0].in (), d[1].in (), out)
         ).run ();

P.H. Welch
See Also:

Constructor Summary
MergeInt(ChannelInputInt[] in, ChannelOutputInt out)
          Construct a new Merge2Int process with the input channels inand the output channel out.
Method Summary
 void run()
          The main body of this process.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail


public MergeInt(ChannelInputInt[] in,
                ChannelOutputInt out)
Construct a new Merge2Int process with the input channels inand the output channel out. The ordering of the input channels makes no difference to the behaviour of this process.

in - the input channels (there must be at least 2)
out - the output channel
Method Detail


public void run()
The main body of this process.

Specified by:
run in interface CSProcess

CSP for Java
(JCSP) 1.1-rc4

Submit a bug or feature to jcsp-team@kent.ac.uk
Version 1.1-rc4 of the JCSP API Specification (Copyright 1997-2008 P.D.Austin and P.H.Welch - All Rights Reserved)
Java is a trademark or registered trademark of Sun Microsystems, Inc. in the US and other countries.