java11-arrays-parallel-methods

Reference: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Arrays.html

preface

• parallelPrefix
  • Cumulates, in parallel, each element of the given array in place,using the supplied function.
  • parallelPrefix​(int[] array, IntBinaryOperator op)
  • parallelPrefix​(int[] array, int fromIndex, int toIndex, IntBinaryOperator op)
  • similar methods for:
    • double[] and DoubleBinaryOperator
    • long[] and LongBinaryOperator
    • T[] and BinaryOperator<T>
• parallelSetAll
  • Set all elements of the specified array, in parallel, using the provided generator function (of index) to compute each element.
  • parallelSetAll​(int[] array, IntUnaryOperator generator)
  • similar methods for:
    • double[] and IntToDoubleFunction
    • long[] and IntToLongFunction
    • T[] and IntFunction<? extends T>
• parallelSort
  • Sorts the specified array into ascending numerical order. The sorting algorithm is a parallel sort-merge that breaks the array into sub-arrays that are themselves sorted and then merged.
  • parallelSort​(int[] a)
  • parallelSort​(int[] a, int fromIndex, int toIndex)
  • similar methods for:
    • byte[]
    • char[]
    • double[]
    • float[]
    • long[]
    • short[]
    • T[]
  • parallelSort​(T[] a, Comparator<? super T> cmp)
  • parallelSort​(T[] a, int fromIndex, int toIndex, Comparator<? super T> cmp)

project description

We provide examples for methods mentioned above:

• accumulate and carry sum across the array

  int[] binaryArray = {0, 0, 1, 0, 1, 1, 1, 0, 1};
  
  Arrays.parallelPrefix(binaryArray, (x, y) -> x + y);
  
  assertThat(binaryArray, is(new int[]{0, 0, 1, 1, 2, 3, 4, 4, 5}));
  

• fill an array that under odd index will be 0 and under even 1

  int[] array = new int[5];
  
  Arrays.parallelSetAll(array, index -> index % 2 == 0 ? 1 : 0);
  
  assertThat(array, is(new int[]{1, 0, 1, 0, 1}));
  

• sort array in parallel way

  int[] array = {5, 3, 4, 0, 1, 2};
  
  Arrays.parallelSort(array);
  
  assertThat(array, is(new int[]{0, 1, 2, 3, 4, 5}));