Stackoverflow Challenge - Integer Counting

This is a challenge focusing on performance and optimization. Details are on the site: https://stackoverflow.com/beta/challenges/79766578/code-challenge-6-integer-counting

How to run?

Install JDK using sdk man:

sdk install java 25-graal

Install hyperfine and coreutils:

brew install hyperfine
brew install coreutils # for gtimeout

To run different solutions use the class name as parameter in evaluate.sh <classname>:

./evaluate.sh Solution1

Solutions are pre-configured to run on 1M record set. See evaluate.sh:

#!/bin/bash

JAVA_VERSION=25
JAVA_VERSION_ID="25-graal"
INPUT_ARGS="./data/1M_random_numbers.txt" # <-- change here if needed
#...

Alternatively, you can generate larger record sets using the provided script, generate.sh:

./generate.sh 100000000 > ./data/100M_random_numbers.txt

Solutions

Single-Threaded - using MappedByteArray

Run evaluate.sh Solution1.

Multi-Threaded - lockless synchronization (CAS)

Run evaluate.sh Solution2.

Multi-Threaded - lock-free via actor-model approach

Run evaluate.sh Solution3.

Single-Threaded - using Java Memory Api (preview in Java 21, released in 25)

Run evaluate.sh Solution4.

Single-Threaded - branchless version, scan four bytes at a time

Run evaluate.sh Solution5.

Comparison (Java 25 GraalVM — JIT Version)

SOLUTION	1M	10M	100M	1B
Single-Threaded - using MappedByteArray	53.8	79.9	348.9	x
Multi-Threaded - lockless synchronization (CAS)	82.2	122.3	625.2	5682
Multi-Threaded - lock-free via actor-model approach	76.9	79.3	117.4	499.9
Single-Threaded - using Java Memory Api	52.6	84.0	406.5	3996
Single-Threaded - branchless version, scan four bytes at a time	55.3	89.4	429.1	x

• Showing elapsed time in ms.
• (x) terminated with error, possibly needs refactoring (against integer overflow, etc.)

Comparison (Java 25 GraalVM — Native)

SOLUTION	1M	10M	100M	1B
Single-Threaded - using MappedByteArray	7.1	33.5	313.8	x
Multi-Threaded - lockless synchronization (CAS)	9.9	56.7	517.1	5115
Multi-Threaded - lock-free via actor-model approach	5.0	10.5	59.4	494.2
Single-Threaded - using Java Memory Api	107.1	917.7	oom	oom
Single-Threaded - branchless version, scan four bytes at a time	8.1	43.0	386.3	x

• Showing elapsed time in ms.
• (x) terminated with an error, possibly needs refactoring (against integer overflow, etc.).
• (oom) Ouf of Memory error, Java Memory Api doesn't play nice with GraalVM Native since memory usage increases excessively.