Computer scienceProgramming languagesKotlinConcurrency and parallelismParallelismBasics of threads

Thread management

Theory

Summing ranges with threads

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The following code is supposed to find the general sum of two inclusive integer ranges in parallel. Unfortunately, this code doesn't work correctly. Try and fix it. Read the comments for a better understanding.

Additional explanations: the implemented class RangeSummator extends Thread and overrides the method run. It sums the range passed to the constructor (left and right limits as integers). The class has a field result that returns the calculated sum or 0 if the thread has not calculated the sum yet.

Sample Input 1: 

1 5
2 4

Sample Output 1: 

24
Write a program in Kotlin
// Fix this function
fun main() {
val (from1Incl, to1Incl) = readLine()!!.split(" ").map { it.toInt() } // limits of the first range
val (from2Incl, to2Incl) = readLine()!!.split(" ").map { it.toInt() } // limits of the second range

val summator1 = RangeSummator(from1Incl, to1Incl) // first summator
val summator2 = RangeSummator(from2Incl, to2Incl) // second summator

val partialSum1 = summator1.result
val partialSum2 = summator2.result
val sum = partialSum1 + partialSum2 // the sum is 0, fix it!
println(sum)
}

// do not change the lines below

val mainThreadId = Thread.currentThread().id

class RangeSummator(var fromIncl: Int, var toIncl: Int) : Thread() {
@Volatile
var result: Long = 0
private set

override fun run() {
val currentId = currentThread().id
if (currentId == mainThreadId) {
throw RuntimeException("You must start a new thread!")
}
var sum: Long = 0
for (i in fromIncl..toIncl) {
sum += i.toLong()
}
result = sum
}
}
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