Simplistic, atomic, interlocked counter that spreads writes across per-thread shards so concurrent updates do not all contend on a single shared value.

Why this exists

ShardedCounter is optimized for write-heavy concurrent scenarios. Each thread writes to its own shard, and reads compute the current total by summing the shard values.

This tradeoff is useful when:

• many threads are updating the counter frequently
• reads are less frequent than writes
• a single Interlocked value becomes a hotspot under contention

Installation

dotnet add package ShardedCounter

Usage

using ShardedCounter.Core;

var counter = new ShardedCounter();

counter.Add(5);
counter.Add(-2);
counter.Increment();
counter.Decrement();

Console.WriteLine(counter.Count); // 3

Public API

public class ShardedCounter
{
    public void Add(long amount);
    public void Increase(long amount);
    public void Decrease(long amount);
    public void Increment();
    public void Decrement();
    public long Count { get; }
}

Add(long amount) is the recommended API because it makes signed counter updates explicit. Increase and Decrease remain available as convenience and compatibility methods.

Target frameworks

The library currently targets:

• net6.0
• net8.0

Notes

• Writes are cheap because they stay on a thread-local shard.
• Reads are more expensive because they sum all known shards.
• This library is best suited to counters that are updated often and read occasionally.

Validation

• Unit tests cover signed updates, compatibility APIs, and concurrent writer scenarios.
• The benchmark project compares ShardedCounter against a plain Interlocked counter under multiple thread counts.

Run the benchmarks with:

dotnet run -c Release --project ShardedCounter.Core.Benchmarks

BenchmarkDotNet will emit markdown and other result artifacts under BenchmarkDotNet.Artifacts/. If you want benchmark snapshots in the repo, rerun the benchmark project intentionally and check in the generated markdown summary you want to preserve.

Releases

• CI runs on pushes and pull requests through .github/workflows/ci.yml.
• NuGet publishing is gated on version tags through .github/workflows/release.yml.
• Create a tag like v6.0.2 after updating package metadata and CHANGELOG.md to publish the next release.