48 lines
1.5 KiB
Java
48 lines
1.5 KiB
Java
// concurrent/Summing.java
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// (c)2017 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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import java.util.stream.*;
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import java.util.function.*;
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import onjava.Timer;
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public class Summing {
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static void timeTest(String id, long checkValue,
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LongSupplier operation) {
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System.out.print(id + ": ");
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Timer timer = new Timer();
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long result = operation.getAsLong();
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if(result == checkValue)
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System.out.println(timer.duration() + "ms");
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else
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System.out.format("result: %d%ncheckValue: %d%n",
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result, checkValue);
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}
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public static final int SZ = 100_000_000;
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// This even works:
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// public static final int SZ = 1_000_000_000;
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public static final long CHECK =
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(long)SZ * ((long)SZ + 1)/2; // Gauss's formula
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public static void main(String[] args) {
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System.out.println(CHECK);
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timeTest("Sum Stream", CHECK, () ->
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LongStream.rangeClosed(0, SZ).sum());
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timeTest("Sum Stream Parallel", CHECK, () ->
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LongStream.rangeClosed(0, SZ).parallel().sum());
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timeTest("Sum Iterated", CHECK, () ->
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LongStream.iterate(0, i -> i + 1)
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.limit(SZ+1).sum());
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// Slower & runs out of memory above 1_000_000:
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// timeTest("Sum Iterated Parallel", CHECK, () ->
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// LongStream.iterate(0, i -> i + 1)
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// .parallel()
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// .limit(SZ+1).sum());
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}
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}
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/* Output:
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5000000050000000
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Sum Stream: 62ms
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Sum Stream Parallel: 42ms
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Sum Iterated: 116ms
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*/
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