CMPS 144L Lab Activity
Computing the Min and Max of an Array using Threads

Here are some Java classes, the first of which it is your task to complete:

• ParallelMinMax: An instance of this (incomplete) Java class identifies the minimum and maximum elements in a given array segment. It does so via a divide-and-conquer algorithm that employs threads.
• ParMinMaxTester: Application program for testing ParallelMinMax. A dialog between the program and a user appears below.
• ParallelArySummer: An instance of this class computes the sum of the elements in a given array segment via a divide-and-conquer algorithm that employs threads. The student should use the source code of this class as a model for completing ParallelMinMax. Indeed, not much needs to be changed to transform one into the other.
• ParArySumTester: Application program for testing ParallelArySummer. You don't need this class, but it is made available in case you wish to experiment with it. It's essentially identical to ParMinMaxTester, except that it employs an instance of ParallelArySummer to compute the sum of an integer array rather than employing an instance of ParallelMinMax to identify the minimum and maximum values within an array.
• RandIntArrayMaker: This class is used by ParMinMaxTester to fill an array with pseudo-randomly generated integers.

Dialog with ParMinMaxTester

User input is shown in boldface. The program first prompts the user to enter the length of the array that is to be the subject of the computation. Then it asks the user to enter lower and upper bounds on the integer values to be placed into the array. Finally, the user provides a seed that is used in establishing an instance of java.util.Random that is used for populating the array with pseudo-randomly generated integer values.

The lines of output that report the minimum and maximum values in specified segments of the array are simply for the purpose of narrating the program's execution, which could aid in debugging.

Each thread produces one such line of output immediately after it has identified the minimum and maximum in the array segment for which it was "responsible". Leaf threads (i.e., ones not having any child threads) describe their segments as SHORT; threads with children describe their segments as LONG.

Whether an array segment is long or short depends upon its length as compared to the class constant LENGTH_THRESHOLD.

Enter array length: 60 Enter lower bound value: -15 Enter upper bound value: 39 Enter random seed: 9 Array: [14, 36, 18, 30, -6, 27, -7, -9, 23, 3, 26, 1, 26, -12, -5, 3, 26, -7, 34, 39, 11, -4, 1, 32, 16, 14, 32, -7, 28, 37, 1, 0, -14, 32, 25, 16, 23, 25, 15, 16, -8, 32, -10, -10, -11, 26, 39, 37, 20, 28, -12, -2, 23, 9, -2, 1, 15, 12, 7, 3] In SHORT range [0..7) the min is -7 and the max is 36 In SHORT range [15..22) the min is -7 and the max is 39 In SHORT range [7..11) the min is -9 and the max is 26 In SHORT range [45..52) the min is -12 and the max is 39 In SHORT range [11..15) the min is -12 and the max is 26 In SHORT range [30..37) the min is -14 and the max is 32 In LONG range [7..15) the min is -12 and the max is 26 In LONG range [0..15) the min is -12 and the max is 36 In SHORT range [52..56) the min is -2 and the max is 23 In SHORT range [56..60) the min is 3 and the max is 15 In SHORT range [37..41) the min is -8 and the max is 25 In SHORT range [41..45) the min is -11 and the max is 32 In SHORT range [22..26) the min is 1 and the max is 32 In LONG range [37..45) the min is -11 and the max is 32 In LONG range [30..45) the min is -14 and the max is 32 In SHORT range [26..30) the min is -7 and the max is 37 In LONG range [22..30) the min is -7 and the max is 37 In LONG range [15..30) the min is -7 and the max is 39 In LONG range [0..30) the min is -12 and the max is 39 In LONG range [52..60) the min is -2 and the max is 23 In LONG range [45..60) the min is -12 and the max is 39 In LONG range [30..60) the min is -14 and the max is 39 In LONG range [0..60) the min is -14 and the max is 39 ParallelMinMax reports that the min and max are -14 and 39