プロコンやるときはプリミティブな配列を使おう

output

Long[]
483.9
long[]
100.0
Long <- long
701.1
long <- Long
184.0

test.kt

import kotlin.system.*
fun main(){
    val N = 3_000
    run{
        val array = Array(N){Array(N){Array(5){0L}}}
        println(array[0][0].javaClass.simpleName)
        val t = average(10){
            for(i in 0 until N){
                for(j in 0 until N){
                    for(k in 0 until 5){
                        array[i][j][k] = array[i][j][k] + 1L
                    }
                }
            }
        }
        println(t)
    }
    run{
        val array = Array(N){Array(N){LongArray(5){0L}}}
        println(array[0][0].javaClass.simpleName)
        val t = average(10){
            for(i in 0 until N){
                for(j in 0 until N){
                    for(k in 0 until 5){
                        array[i][j][k] = array[i][j][k] + 1L
                    }
                }
            }
        }
        println(t)
    }
    run{
        println("Long <- long")
        val array = Array(N){Array(N){Array(5){0L}}}
        val longArray = Array(N){Array(N){LongArray(5){0L}}}
        val t = average(10){
            for(i in 0 until N){
                for(j in 0 until N){
                    for(k in 0 until 5){
                        array[i][j][k] = longArray[i][j][k] + 1L
                    }
                }
            }
        }
        println(t)
    }
    run{
        println("long <- Long")
        val array = Array(N){Array(N){Array(5){0L}}}
        val longArray = Array(N){Array(N){LongArray(5){0L}}}
        val t = average(10){
            for(i in 0 until N){
                for(j in 0 until N){
                    for(k in 0 until 5){
                        longArray[i][j][k] = array[i][j][k] + 1L
                    }
                }
            }
        }
        println(t)
    }
}

fun average(n: Int, block: () -> Unit) = (1..n).map{
    measureTimeMillis{
        block()
    }
}.average()

アンボクシングは大したことないけどボクシングが発生するとかなり時間かかる