SIMD is not enabled?

[MyErpSoft]

package sample

//import kotlin.random.Random
import kotlin.system.measureNanoTime

fun hello(): String = "Hello, Kotlin/Native!"

fun main() {
    runIt()
}

private fun runIt(){
    var sum = 0
    val time = measureNanoTime{
        //val ran = Random.Default
        for (i in 0 until 1_0000_0000){
            //val v = ran.nextInt()
            sum += getInt32TrueCount2(i)
        }
    }

    println("time：$time ns, result: $sum")
}

private fun getInt32TrueCount(value: Int):Int {
    if (value == 0) {
        return 0
    }

    return getByteTrueCount(value and 0xFF) +
            getByteTrueCount((value shr 8) and 0xFF) +
            getByteTrueCount((value shr 16) and 0xFF) +
            getByteTrueCount((value shr 24) and 0xFF)
}

private fun getByteTrueCount(value: Int) : Int{
    if(value== 0){
        return 0
    }

    val a = (value and 0x1)
    val b = ((value and 0x2)  shr 1)
    val c = ((value and 0x4)  shr 2)
    val d = ((value and 0x8)  shr 3)
    val e = ((value and 0x10) shr 4)
    val f = ((value and 0x20) shr 5)
    val g = ((value and 0x40) shr 6)
    val h = ((value and 0x80) shr 7)

    return a + b + c + d + e + f + g + h
}

private fun getInt32TrueCount2(value: Int):Int {
    if (value == 0) {
        return 0
    }

    return getByteTrueCount2(value and 0xFF) +
            getByteTrueCount2((value shr 8) and 0xFF) +
            getByteTrueCount2((value shr 16) and 0xFF) +
            getByteTrueCount2((value shr 24) and 0xFF)
}

private val m1 = intArrayOf(0x1,0x2,0x4,0x8,0x10,0x20,0x40,0x80)
private val m2 = intArrayOf(0,1,2,3,4,5,6,7)
private val m3 = IntArray(8)

private fun getByteTrueCount2(value : Int) : Int{
    if (value == 0) {
        return 0
    }

    var sum = 0
    for (i in 0 until m1.size){
        sum += (value and m1[i] shr i)
    }

    return sum
}

Kotlin Native : ~ 80 s
Kotlin JVM : ~ 1.3 s

Windows 10 64 位
Intel Core i5-6500 @3.2GHz 4 Core
16GB RAM
Kotlin native 1.3.21

Why is the getByteTrueCount2 method so slow?

[MyErpSoft]

Bound checking elimination #1791

[SvyatoslavScherbina]

for (i in 0 until m1.size){
sum += (value and m1[i] shr i)

m1 is global variable, and accesses to global variables are noticeably more expensive than to local ones.

Extracting m1 to a local variable should help a bit.

Also please note: https://github.com/JetBrains/kotlin-native/blob/master/RELEASE_NOTES.md#performance

[olonho]

If goal is to write faster code, it makes sense to do it in the way suitable for the platform. In your case program with following modifications

package sample

import sample.interop1.*
import kotlin.system.measureNanoTime
import kotlin.random.Random

private fun runIt() {
    var sum = 0
    val time = measureNanoTime {
        //val ran = Random.Default
        for (i in 0 until 1_0000_0000){
            //val v = ran.nextInt()
            sum += getInt32TrueCount2(i)
        }
    }

    println("time：${time.toFloat() / 1_000_000_000} s, result: $sum")
}

private fun runItFaster() {
    var sum = 0
    val time = measureNanoTime {
        for (i in 0 until 1_0000_0000){
            sum += popcount(i)
        }
    }

    println("time：${time.toFloat() / 1_000_000_000} s, result: $sum")
}

private fun getInt32TrueCount(value: Int):Int {
    if (value == 0) {
        return 0
    }

    return getByteTrueCount(value and 0xFF) +
            getByteTrueCount((value shr 8) and 0xFF) +
            getByteTrueCount((value shr 16) and 0xFF) +
            getByteTrueCount((value shr 24) and 0xFF)
}

private fun getByteTrueCount(value: Int) : Int{
    if(value== 0){
        return 0
    }

    val a = (value and 0x1)
    val b = ((value and 0x2)  shr 1)
    val c = ((value and 0x4)  shr 2)
    val d = ((value and 0x8)  shr 3)
    val e = ((value and 0x10) shr 4)
    val f = ((value and 0x20) shr 5)
    val g = ((value and 0x40) shr 6)
    val h = ((value and 0x80) shr 7)

    return a + b + c + d + e + f + g + h
}

private fun getInt32TrueCount2(value: Int):Int {
    if (value == 0) {
        return 0
    }

    return getByteTrueCount2(value and 0xFF) +
            getByteTrueCount2((value shr 8) and 0xFF) +
            getByteTrueCount2((value shr 16) and 0xFF) +
            getByteTrueCount2((value shr 24) and 0xFF)
}

private val m1 = intArrayOf(0x1,0x2,0x4,0x8,0x10,0x20,0x40,0x80)
private val m2 = intArrayOf(0,1,2,3,4,5,6,7)
private val m3 = IntArray(8)

private fun getByteTrueCount2(value : Int) : Int{
    if (value == 0) {
        return 0
    }

    var sum = 0
    for (i in 0 until m1.size){
        sum += (value and m1[i] shr i)
    }

    return sum
}

fun main() {
    runIt()
    runItFaster()
}

And with following .def file

package=sample.interop1
---
#include <stdint.h>
int32_t popcount(int32_t x) {
   return __builtin_popcount(x);
}

prints on my machine

time：16.690422 s, result: 1314447104
time：0.3516291 s, result: 1314447104

[olonho]

Same code on JVM produces

time：1.0619177 s, result: 1314447104

which makes Native about 3 times faster on that task.

[MyErpSoft]

Cool!
I learned something new. Thank you.