51 lines
1.6 KiB
Java
51 lines
1.6 KiB
Java
// threads/Summing.java
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// (c)2016 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://mindviewinc.com/Books/OnJava/ for more book information.
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import java.util.stream.*;
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import java.util.function.*;
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public class Summing {
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static volatile long x;
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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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long t = System.currentTimeMillis();
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long result = operation.getAsLong();
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long duration = System.currentTimeMillis() - t;
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if(result == checkValue)
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System.out.println(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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x = result; // Prevent optimization
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}
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public static int SZ = 100_000_000;
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// This even works:
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// public static int SZ = 1_000_000_000;
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// Gauss's formula:
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public static final long CHECK =
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(long)SZ * ((long)SZ + 1)/2;
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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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// Takes longer, 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: 631ms
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Sum Stream Parallel: 159ms
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Sum Iterated: 2560ms
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*/
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