concurrent/Summing3.java · ThisYoung/OnJava8-Examples

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OnJava8-Examples

concurrent

Summing3.java

Summing3.java 1.21 KB

// concurrent/Summing3.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// {ExcludeFromTravisCI}
import java.util.*;

public class Summing3 {
 static long basicSum(Long[] ia) {
 long sum = 0;
 int size = ia.length;
 for(int i = 0; i < size; i++)
 sum += ia[i];
 return sum;
 }
 // Approximate largest value of SZ before
 // running out of memory on my machine:
 public static final int SZ = 10_000_000;
 public static final long CHECK =
 (long)SZ * ((long)SZ + 1)/2;
 public static void main(String[] args) {
 System.out.println(CHECK);
 Long[] aL = new Long[SZ+1];
 Arrays.parallelSetAll(aL, i -> (long)i);
 Summing.timeTest("Long Array Stream Reduce",
 CHECK, () ->
 Arrays.stream(aL).reduce(0L, Long::sum));
 Summing.timeTest("Long Basic Sum", CHECK, () ->
 basicSum(aL));
 // Destructive summation:
 Summing.timeTest("Long parallelPrefix",CHECK, ()-> {
 Arrays.parallelPrefix(aL, Long::sum);
 return aL[aL.length - 1];
 });
 }
}
/* Output:
50000005000000
Long Array Stream Reduce: 1038ms
Long Basic Sum: 21ms
Long parallelPrefix: 3616ms
*/

一键复制编辑原始数据按行查看历史

Bruce Eckel 提交于 2017年05月14日 14:01 +08:00 . Summing3 doesn't work with Travis CI

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

// concurrent/Summing3.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// {ExcludeFromTravisCI}
import java.util.*;

public class Summing3 {
 static long basicSum(Long[] ia) {
 long sum = 0;
 int size = ia.length;
 for(int i = 0; i < size; i++)
 sum += ia[i];
 return sum;
 }
 // Approximate largest value of SZ before
 // running out of memory on my machine:
 public static final int SZ = 10_000_000;
 public static final long CHECK =
 (long)SZ * ((long)SZ + 1)/2;
 public static void main(String[] args) {
 System.out.println(CHECK);
 Long[] aL = new Long[SZ+1];
 Arrays.parallelSetAll(aL, i -> (long)i);
 Summing.timeTest("Long Array Stream Reduce",
 CHECK, () ->
 Arrays.stream(aL).reduce(0L, Long::sum));
 Summing.timeTest("Long Basic Sum", CHECK, () ->
 basicSum(aL));
 // Destructive summation:
 Summing.timeTest("Long parallelPrefix",CHECK, ()-> {
 Arrays.parallelPrefix(aL, Long::sum);
 return aL[aL.length - 1];
 });
 }
}
/* Output:
50000005000000
Long Array Stream Reduce: 1038ms
Long Basic Sum: 21ms
Long parallelPrefix: 3616ms
*/