Jetpack Compose mutableStateList vs mutableList Performance

Question

How do mutableState, mutableStateList, mutableStateMap perform in comparison to a normal variable, mutableList, mutableMap? If there are observers listening they will be slower of course (because recomposition is triggered) but is there a difference between them if there are no observers at all?

Thanks in advance.

Answer 1

In the end I wrote a simple class to test the performances:

import androidx.compose.runtime.mutableStateListOf
import androidx.compose.runtime.mutableStateOf


fun main() {
    val numbers = 1000000
    for (i in 1 until 11) {
        println("test number $i")

        testNormalVariable(numbers)
        testStateVariable(numbers)
        testNormalList(numbers)
        testStateList(numbers)

        println()
    }
}

fun testNormalVariable(numbers: Int) {
    var normalVariable = 0
    val startTime = System.currentTimeMillis()
    for (i in 0 until numbers) {
        normalVariable = i
    }
    val time = System.currentTimeMillis() - startTime
    println("testNormalVariable took $time ms")
}

fun testStateVariable(numbers: Int) {
    val stateVariable = mutableStateOf(0)
    val startTime = System.currentTimeMillis()
    for (i in 0 until numbers) {
        stateVariable.value = i
    }
    val time = System.currentTimeMillis() - startTime
    println("testStateVariable took $time ms")
}

fun testNormalList(numbers: Int) {
    val normalList = mutableListOf<Int>()
    val startTime = System.currentTimeMillis()
    for (i in 0 until numbers) {
        normalList.add(i)
    }
    val time = System.currentTimeMillis() - startTime
    println("testNormalList took $time ms")
}

fun testStateList(numbers: Int) {
    val stateList = mutableStateListOf<Int>()
    val startTime = System.currentTimeMillis()
    for (i in 0 until numbers) {
        stateList.add(i)
    }
    val time = System.currentTimeMillis() - startTime
    println("testStateList took $time ms")
}

And it became clear that mutableState and mutableStateList are significantly slower than a normal variable or a mutableList:

test number 1
testNormalVariable took 5 ms
testStateVariable took 82 ms
testNormalList took 48 ms
testStateList took 366 ms

test number 2
testNormalVariable took 5 ms
testStateVariable took 94 ms
testNormalList took 121 ms
testStateList took 368 ms

test number 3
testNormalVariable took 0 ms
testStateVariable took 35 ms
testNormalList took 30 ms
testStateList took 319 ms

test number 4
testNormalVariable took 0 ms
testStateVariable took 27 ms
testNormalList took 25 ms
testStateList took 299 ms

test number 5
testNormalVariable took 0 ms
testStateVariable took 32 ms
testNormalList took 29 ms
testStateList took 289 ms

test number 6
testNormalVariable took 0 ms
testStateVariable took 26 ms
testNormalList took 20 ms
testStateList took 310 ms

test number 7
testNormalVariable took 0 ms
testStateVariable took 41 ms
testNormalList took 30 ms
testStateList took 413 ms

test number 8
testNormalVariable took 0 ms
testStateVariable took 25 ms
testNormalList took 28 ms
testStateList took 142 ms

test number 9
testNormalVariable took 0 ms
testStateVariable took 93 ms
testNormalList took 29 ms
testStateList took 298 ms

test number 10
testNormalVariable took 0 ms
testStateVariable took 46 ms
testNormalList took 32 ms
testStateList took 309 ms