Kotlin Parallel performance examples.

MainActivity.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar)

        fab.setOnClickListener { view ->
            main()
        }
    }
}

fun main() {
    Thread {
        log("many thread start")
        measureTimeMillis {
            manyTask1(400)
//            manyTask2(400)
//            manyTask3(400)
//            manyTask4(400)
//            manyTask5(400)
//            manyTask6(400)
        }.also {
            log("[cost]: ${it}")
        }
    }.start()
}

fun manyTask1(num: Int) {
    val latch = CountDownLatch(num)
    (0..num).forEach { _ ->
        Thread {
            TimeUnit.MILLISECONDS.sleep(100)
            latch.countDown()
        }.start()
    }
    latch.await()
}


fun manyTask2(num: Int) {
    val latch = CountDownLatch(num)
    val executor = Executors.newScheduledThreadPool(4)
    (0..num).forEach { _ ->
        executor.execute {
            TimeUnit.MILLISECONDS.sleep(100)
            latch.countDown()
        }
    }
    latch.await()
}

fun manyTask3(num: Int) {
    val latch = CountDownLatch(num)
    val executor = AsyncTask.THREAD_POOL_EXECUTOR
    (0..num).forEach { _ ->
        executor.execute {
            TimeUnit.MILLISECONDS.sleep(100)
            latch.countDown()
        }
    }
    latch.await()
}

fun manyTask4(num: Int) {
    runBlocking {
        (0..num).toList().map {
            suspend {
                delay(100)
            }
        }.forEach {
            launch(Dispatchers.Unconfined) {
                withContext(IO) { it() }
            }
        }
    }
}

fun manyTask6(num: Int) {
    runBlocking {
        (0..num).toList().map {
            suspend {
                delay(100)
            }
        }.forEach {
            launch(Dispatchers.Default) {
                withContext(IO) { it() }
            }
        }
    }
}

fun manyTask5(num: Int) {
    runBlocking {
        (0..num).map {
            async(IO) {
                suspend {
                    delay(100)
                }()
            }
        }.awaitAll()
    }
}

fun log(msg: String) {
    println("[ababab] $msg")
//    Log.d("ababab", msg)
}

android {
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}
dependencies {
    // async// kotlin coroutines
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.1.1"
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.1.1"
}