44 lines
1.2 KiB
Java
44 lines
1.2 KiB
Java
// concurrent/Summing2.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.*;
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public class Summing2 {
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static long basicSum(long[] ia) {
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long sum = 0;
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int size = ia.length;
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for(int i = 0; i < size; i++)
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sum += ia[i];
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return sum;
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}
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// Approximate largest value of SZ before
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// running out of memory on my machine:
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public static final int SZ = 20_000_000;
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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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long[] la = new long[SZ+1];
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Arrays.parallelSetAll(la, i -> i);
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Summing.timeTest("Array Stream Sum", CHECK, () ->
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Arrays.stream(la).sum());
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Summing.timeTest("Parallel", CHECK, () ->
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Arrays.stream(la).parallel().sum());
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Summing.timeTest("Basic Sum", CHECK, () ->
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basicSum(la));
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// Destructive summation:
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Summing.timeTest("parallelPrefix", CHECK, () -> {
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Arrays.parallelPrefix(la, Long::sum);
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return la[la.length - 1];
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});
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}
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}
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/* Output:
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200000010000000
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Array Stream Sum: 22ms
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Parallel: 21ms
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Basic Sum: 16ms
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parallelPrefix: 116ms
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*/
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