Package org.jcsp.plugNplay
Class Merge
- java.lang.Object
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- org.jcsp.plugNplay.Merge
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- All Implemented Interfaces:
CSProcess
public final class Merge extends java.lang.Object implements CSProcess
Merges an array of strictly increasing Integer input streams into one strictly increasing output stream.Process Diagram
Description
Merge 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 Integers 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[] java.lang.Number Assume: in.length >= 2.
All channels can accept data from any subclass of Number. It is possible to send Floats down one channel and Integers down the other. However all values will be converted to ints.Output Channels out java.lang.Integer The output will always be of type Integer. Example
The following example shows how to use Merge 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.*; import org.jcsp.plugNplay.*; public class MergeExample { public static void main (String[] argv) { final One2OneChannel[] a = Channel.one2oneArray (5); final One2OneChannel[] b = Channel.one2oneArray (4, new InfiniteBuffer ()); final One2OneChannel c = Channel.one2one (); final One2OneChannel d = Channel.one2one (); new Parallel ( new CSProcess[] { new Mult (2, a[0].in (), b[0].out ()), new Mult (3, a[1].in (), b[1].out ()), new Mult (5, a[2].in (), b[2].out ()), new Mult (7, a[3].in (), b[3].out ()), new Merge (Channel.getInputArray (b), c.out ()), new Prefix (1, c.in (), d.out ()), new Delta (d.in (), Channel.getOutputArray (a)), new Printer (a[4].in (), "--> ", "\n") } ).run (); } }
Implementation Note
The implementation sets up a balanced binary tree of parallel Merge2 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 Merge2 (in[0], in[1], out).run (); break; case 3: final One2OneChannel c = Channel.one2one(); new Parallel ( new CSProcess[] { new Merge2 (in[0], in[1], c.out ()), new Merge2 (c.in (), in[2], out) } ).run (); break; default: // deduce: n >= 4 final int n2 = n/2; ChannelInput[] bottom = new ChannelInput[n2]; ChannelInput[] top = new ChannelInput[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 One2OneChannel[] d = Channel.one2oneArray(2); new Parallel ( new CSProcess[] { new Merge (bottom, d[0].out ()), new Merge (top, d[1].out ()), new Merge2 (d[0].in (), d[1].in (), out) } ).run (); break; } }
- See Also:
Merge2
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Field Summary
Fields Modifier and Type Field Description private ChannelInput[]
in
The input channelsprivate ChannelOutput
out
The output channel
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Constructor Summary
Constructors Constructor Description Merge(ChannelInput[] in, ChannelOutput out)
Construct a new Merge2 process with the input channels inand the output channel out.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
run()
The main body of this process.
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Field Detail
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in
private final ChannelInput[] in
The input channels
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out
private final ChannelOutput out
The output channel
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Constructor Detail
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Merge
public Merge(ChannelInput[] in, ChannelOutput out)
Construct a new Merge2 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.- Parameters:
in
- the input channels (there must be at least 2)out
- the output channel
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