Advent of Code 2019 in Multi-Platform Kotlin

Intro

In 2020, I will be participating in the Advent of Code using Kotlin multi-platform code only. This means I can run my solutions on the JVM, on Node JS and natively on Windows. I did the same in 2019 and 2018. Each year the Kotlin platform has evolved, so it's interesting to see how the relative performance of these build targets evolve. Just to spice things up, this year I'll be using GraalVM to run the JVM versions, and perhaps also the Node implementation of GraalVM if I find the time.

I will be measuring the performance of each platform by measuring the elapsed time calculating the solution N times:

val times = (1..repeat).map {
    measureNanos {
        Puzzles.run(day, part)
    }
}

where repeat is the number of desired repetitions, and day and part are used to select the proper challenge.

Note that the measureNanos function is the first example of functionality that isn't available in common code, since measuring time is platform-specific. The function is implemented using Kotlin's expext/actual mechanism.

Runner.kt defines its expectation of a function measureNanos for each supported platform with the signature:

expect inline fun measureNanos(block: () -> Unit): Long

Each platform provides an actual implementation in files called Actuals.kt. On the JVM and native, we can use measureNanoTime as provided by the Kotlin standard library on these platforms:

JVM and Native:

actual inline fun measureNanos(block: () -> Unit) = measureNanoTime(block)

On Node, we need to write our own implementation:

actual inline fun measureNanos(block: () -> Unit): Long {
    val start = process.hrtime()
    block()
    val end = process.hrtime(start)
    val nanos = (end[0] * 1e9 + end[1]) as Double
    return nanos.roundToLong()
}

Usually, I try to finish a puzzle as quickly as possible, then spend some time to cleanup and optimise the code. If and when these optimizations alter the performance, I'll update the measurements below to reflect the new solution.

Important

There is a very explicit warning in the FAQ of Kotlin/Native that says the current version of Kotlin/Native is not suited for performance analysis, as it has not been optimised in any way for performance and benchmarking.

Apart from that, all measurements were taken on my laptop, under non-controlled circumstances using non-optimized code and tools. So, if you use the results below for anything important, you're insane...

Day 1

Today I had a lot of trouble getting everything compiling and running. First, somehow my IntelliJ run configuration for the JVM had somehow been corrupted which took me ages to discover, and then there was an issue with the native runner.

Platform	Average (ms)	Measurements (ms)
GraalVM	21 ± 20	99, 30, 25, 41, 20, 31, 16, 10, 15, 10, 15, 11, 11, 11, 12, 12, 12, 11, 11, 13
Node JS	14.5 ± 14.8	70, 35, 31, 12, 9, 8, 9, 8, 7, 11, 9, 9, 8, 8, 8, 9, 8, 7, 7, 8
Native	147 ± 9.7	158, 143, 132, 141, 143, 142, 141, 152, 171, 143, 142, 146, 144, 144, 137, 149, 150, 137, 150, 170

Day 2

Platform	Average (ms)	Measurements (ms)
GraalVM	9.1 ± 14.7	71, 16, 11, 7, 7, 6, 5, 5, 5, 8, 4, 5, 2, 3, 3, 4, 2, 2, 4, 4
Node JS	17.4 ± 18.6	90, 43, 25, 20, 12, 10, 8, 8, 9, 8, 9, 8, 8, 8, 19, 11, 11, 11, 9, 11
Native	39.1 ± 7.5	36, 36, 37, 34, 34, 36, 34, 45, 41, 68, 34, 42, 36, 35, 42, 34, 38, 35, 41, 34

Day 3

Platform	Average (ms)	Measurements (ms)
GraalVM	5.7 ± 11.1	53, 7, 4, 4, 2, 5, 5, 4, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1
Node JS	13.1 ± 17.0	73, 41, 34, 11, 7, 9, 6, 10, 6, 7, 6, 5, 6, 8, 5, 3, 3, 4, 4, 4
Native	25.2 ± 6.4	20, 20, 29, 31, 22, 17, 36, 17, 30, 26, 20, 18, 31, 22, 33, 27, 25, 18, 36, 17

Day 4

Platform	Average (ms)	Measurements (ms)
GraalVM	11.3 ± 14,5	70, 21, 16, 17, 10, 10, 8, 11, 6, 6, 5, 5, 4, 4, 6, 5, 3, 4, 3, 2
Node JS	14.8 ± 13.5	65, 26, 35, 17, 8, 8, 9, 7, 7, 8, 8, 8, 12, 8, 8, 12, 10, 12, 10, 8
Native	56.2 ± 6.0	53, 69, 51, 51, 47, 60, 59, 47, 56, 49, 52, 56, 53, 57, 62, 65, 56, 48, 64, 57

Day 5

Platform	Average (ms)	Measurements (ms)
GraalVM	3.9 ± 6.0	29, 5, 2, 2, 2, 2, 4, 3, 2, 2, 2, 1, 1, 1, 2, 1, 1, 1, 5, 1
Node JS	8.8 ± 8.1	35, 24, 13, 17, 8, 9, 4, 4, 4, 5, 3, 5, 4, 5, 5, 3, 4, 3, 4, 5
Native	18.9 ± 2.6	18, 18, 16, 19, 18, 18, 27, 18, 18, 16, 18, 16, 19, 17, 22, 16, 18, 17, 22, 17

Day 6

Platform	Average (ms)	Measurements (ms)
GraalVM	7.4 ± 10.7	52, 10, 11, 12, 7, 5, 8, 6, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
Node JS	19.4 ± 21. 0	108, 29, 20, 22, 13, 11, 11, 11, 14, 13, 15, 16, 13, 12, 11, 15, 9, 12, 10, 14
Native	58.5 ± 5.0	64, 61, 63, 55, 58, 56, 65, 54, 56, 58, 72, 62, 54, 52, 54, 55, 59, 52, 52, 59

Day 7

Platform	Average (ms)	Measurements (ms)
GraalVM	84 ± 71	390, 83, 68, 66, 62, 63, 61, 60, 73, 85, 71, 77, 62, 63, 73, 65, 62, 61, 60, 60
Node JS	1679 ± 142	1723, 1726, 1628, 1657, 1517, 1843, 1748, 1988, 2061, 1620, 1614, 1730, 1646, 1606, 1686, 1577, 1567, 1555, 1506, 1568
Native	4721 ± 383	4417, 4235, 4648, 4426, 4581, 5086, 4806, 5037, 4304, 5537, 4693, 5095, 4679, 5624, 4955, 4457, 4256, 4552, 4506, 4508

Day 8

Platform	Average (ms)	Measurements (ms)
GraalVM	8.7 ± 9.5	47, 15, 16, 7, 5, 5, 3, 4, 5, 6, 5, 5, 7, 5, 5, 5, 5, 6, 6, 4
Node JS	23.3 ± 14.1	81, 37, 20, 22, 24, 17, 20, 17, 18, 23, 15, 18, 17, 18, 15, 16, 16, 20, 19, 23
Native	124 ± 17	106, 134, 141, 112, 136, 105, 139, 106, 134, 107, 153, 108, 128, 135, 117, 119, 154, 90, 118, 124

Day 9

Platform	Average (ms)	Measurements (ms)
GraalVM	32.6 ± 36.3	183, 68, 41, 25, 18, 19, 21, 19, 26, 20, 24, 18, 24, 20, 18, 20, 19, 18, 26, 17
Node JS	32.5 ± 22.5	118, 57, 59, 33, 32, 22, 24, 29, 21, 20, 20, 21, 21, 20, 24, 24, 21, 25, 21, 26
Native	105 ± 3.7	103, 106, 106, 102, 109, 108, 100, 100, 105, 108, 100, 106, 114, 109, 107, 105, 106, 100, 107, 101

Day 10

Platform	Average (µs)	Measurements (µs)
GraalVM	2483 ± 5719	27370, 1606, 1629, 1394, 1368, 1281, 1475, 1500, 1343, 1276, 1303, 1243, 1274, 1177, 708, 489, 588, 1031, 831, 760
Node JS	6837 ± 8230	35319, 12176, 6247, 5928, 6658, 6698, 2986, 3525, 24430, 2477, 3497, 3641, 3060, 2472, 2099, 1761, 1379, 5845, 3452, 3080
Native	2432 ± 669	2581, 2194, 2174, 3230, 2548, 2318, 2854, 1781, 1830, 1770, 3586, 1858, 2007, 3387, 2382, 2218, 4189, 1826, 1841, 2067