concurrent/Summing.java · ThisYoung/OnJava8-Examples

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OnJava8-Examples

concurrent

Summing.java

Summing.java 1.50 KB

// concurrent/Summing.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.
import java.util.stream.*;
import java.util.function.*;
import onjava.Timer;

public class Summing {
 static void timeTest(String id, long checkValue,
 LongSupplier operation) {
 System.out.print(id + ": ");
 Timer timer = new Timer();
 long result = operation.getAsLong();
 if(result == checkValue)
 System.out.println(timer.duration() + "ms");
 else
 System.out.format("result: %d%ncheckValue: %d%n",
 result, checkValue);
 }
 public static final int SZ = 100_000_000;
 // This even works:
 // public static final int SZ = 1_000_000_000;
 public static final long CHECK =
 (long)SZ * ((long)SZ + 1)/2; // Gauss's formula
 public static void main(String[] args) {
 System.out.println(CHECK);
 timeTest("Sum Stream", CHECK, () ->
 LongStream.rangeClosed(0, SZ).sum());
 timeTest("Sum Stream Parallel", CHECK, () ->
 LongStream.rangeClosed(0, SZ).parallel().sum());
 timeTest("Sum Iterated", CHECK, () ->
 LongStream.iterate(0, i -> i + 1)
 .limit(SZ+1).sum());
 // Slower & runs out of memory above 1_000_000:
 // timeTest("Sum Iterated Parallel", CHECK, () ->
 // LongStream.iterate(0, i -> i + 1)
 // .parallel()
 // .limit(SZ+1).sum());
 }
}
/* Output:
5000000050000000
Sum Stream: 167ms
Sum Stream Parallel: 46ms
Sum Iterated: 284ms
*/

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11日 01:45 +08:00 . Narrowed listing widths, fixed output

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 43 44 45 46 47

// concurrent/Summing.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.
import java.util.stream.*;
import java.util.function.*;
import onjava.Timer;

public class Summing {
 static void timeTest(String id, long checkValue,
 LongSupplier operation) {
 System.out.print(id + ": ");
 Timer timer = new Timer();
 long result = operation.getAsLong();
 if(result == checkValue)
 System.out.println(timer.duration() + "ms");
 else
 System.out.format("result: %d%ncheckValue: %d%n",
 result, checkValue);
 }
 public static final int SZ = 100_000_000;
 // This even works:
 // public static final int SZ = 1_000_000_000;
 public static final long CHECK =
 (long)SZ * ((long)SZ + 1)/2; // Gauss's formula
 public static void main(String[] args) {
 System.out.println(CHECK);
 timeTest("Sum Stream", CHECK, () ->
 LongStream.rangeClosed(0, SZ).sum());
 timeTest("Sum Stream Parallel", CHECK, () ->
 LongStream.rangeClosed(0, SZ).parallel().sum());
 timeTest("Sum Iterated", CHECK, () ->
 LongStream.iterate(0, i -> i + 1)
 .limit(SZ+1).sum());
 // Slower & runs out of memory above 1_000_000:
 // timeTest("Sum Iterated Parallel", CHECK, () ->
 // LongStream.iterate(0, i -> i + 1)
 // .parallel()
 // .limit(SZ+1).sum());
 }
}
/* Output:
5000000050000000
Sum Stream: 167ms
Sum Stream Parallel: 46ms
Sum Iterated: 284ms
*/