EpochSim

Deterministic tick simulation engine for .NET 10.

Recommended package for embedding:

dotnet add package EpochSim

EpochSim.All is useful when you want one dependency that brings the full module graph (EpochSim, Execution, Serialization, Observability, Kernel):

dotnet add package EpochSim.All

Russian version: README.ru.md

State-Only Quickstart (No Events, No Codecs)

using EpochSim;

var state = new WorldState();
var engine = Epoch.CreateEngine<WorldState>();
engine.AddSystem("World", tick: ctx => ctx.State.Population++);

using var run = Epoch.QuickRun(state, rootDir: "artifacts");
engine.Attach(run);
engine.RunTicks(state, seed: 1, endTickInclusive: 100);

Console.WriteLine(state.Population);

public sealed class WorldState
{
    public int Population { get; set; }
}

This is the fastest path: useful artifacts, deterministic run, almost zero wiring.

Recommended Artifacts

QuickRun:

Best for first use and basic debugging.
Enables deterministic run metadata + snapshots + state fingerprints + trace.
No event codec required.

using var run = Epoch.QuickRun(state, rootDir: "artifacts");

RecommendedRun:

Best for real debugging in apps and services.
Enables fingerprints + snapshots + trace + profiling + failure artifacts.
No codec required for this baseline.
Add invariants when needed.

using var run = Epoch.RecommendedRun(state, rootDir: "artifacts", invariants: null);

Advanced overloads stay available when you want full control:

Epoch.RecommendedRun(state, codec, serializer, rootDir, invariants)
EpochSimRun.For(state)...Build()

Event Log / Replay (Use When You Need Replay/Bisect)

Event log is optional and intended for replay workflows (verify-run, bisect, fast-replay).

using EpochSim;
using EpochSim.Kernel.Messaging;

var codec = Epoch.JsonCodecFromAssembly<Program>(t => t == typeof(Changed));
var serializer = Epoch.JsonStateSerializer<WorldState>();

using var run = Epoch.RecommendedRun(state, codec, serializer, rootDir: "artifacts");

[MessageKind("Changed")]
public sealed record Changed(int Delta) : IEvent;

RunTicks vs Session

Use RunTicks for batch jobs:

engine.RunTicks(state, seed: 1, endTickInclusive: 1000);

Use SimulationSession<TState> for long-lived loops (games, servers, interactive stepping):

var inbox = new CommandInbox();
engine.AttachInbox(inbox);

using var session = engine.CreateSession(state, seed: 1, startTick: 0);
inbox.Enqueue(new AddPopulation(5));
session.TickOnce();
session.RunUntil(100);

using EpochSim.Kernel.Messaging;
[MessageKind("AddPopulation")]
public sealed record AddPopulation(int Delta) : ICommand;

External Input Pattern (HTTP/UI/Queue -> Sim)

Use inboxes to feed external commands deterministically into the sim thread:

CommandInbox: commands for the next tick.
ScheduledCommandInbox: commands scheduled at a specific tick with stable ordering:
- primary key: tick ascending
- secondary key: insertion order

var scheduled = new ScheduledCommandInbox();
engine.AttachScheduledInbox(scheduled);

scheduled.Enqueue(10, new AddPopulation(3));
scheduled.Enqueue(10, new AddPopulation(7));
scheduled.Enqueue(12, new AddPopulation(1));

See full integration recipes: Embedding

CLI Onboarding

Create a starter app:

dotnet run --project src/EpochSim.Cli -- init .

Run and inspect artifacts:

dotnet run --project src/EpochSim.Cli -- run artifacts
dotnet run --project src/EpochSim.Cli -- list-runs artifacts
dotnet run --project src/EpochSim.Cli -- inspect-run artifacts <runId>

Determinism debugging:

dotnet run --project src/EpochSim.Cli -- verify-run artifacts <runId>
dotnet run --project src/EpochSim.Cli -- bisect artifacts <runId>

Samples

Recommended simple sample: src/EpochSim.Samples/Quickstart/QuickstartSample.cs
Advanced/legacy domain sample: src/EpochSim.Samples/Population/ (event-heavy diagnostic domain)

Build and Test

dotnet build EpochSim.slnx -m:1
dotnet test EpochSim.slnx -m:1

Docs

English:

Russian:

EpochSim

Deterministic tick simulation engine for .NET 10.

Recommended package for embedding:

dotnet add package EpochSim

EpochSim.All is useful when you want one dependency that brings the full module graph (EpochSim, Execution, Serialization, Observability, Kernel):

dotnet add package EpochSim.All

Russian version: README.ru.md

State-Only Quickstart (No Events, No Codecs)

using EpochSim;

var state = new WorldState();
var engine = Epoch.CreateEngine<WorldState>();
engine.AddSystem("World", tick: ctx => ctx.State.Population++);

using var run = Epoch.QuickRun(state, rootDir: "artifacts");
engine.Attach(run);
engine.RunTicks(state, seed: 1, endTickInclusive: 100);

Console.WriteLine(state.Population);

public sealed class WorldState
{
    public int Population { get; set; }
}

This is the fastest path: useful artifacts, deterministic run, almost zero wiring.

Recommended Artifacts

QuickRun:

Best for first use and basic debugging.
Enables deterministic run metadata + snapshots + state fingerprints + trace.
No event codec required.

using var run = Epoch.QuickRun(state, rootDir: "artifacts");

RecommendedRun:

Best for real debugging in apps and services.
Enables fingerprints + snapshots + trace + profiling + failure artifacts.
No codec required for this baseline.
Add invariants when needed.

using var run = Epoch.RecommendedRun(state, rootDir: "artifacts", invariants: null);

Advanced overloads stay available when you want full control:

Epoch.RecommendedRun(state, codec, serializer, rootDir, invariants)
EpochSimRun.For(state)...Build()

Event Log / Replay (Use When You Need Replay/Bisect)

Event log is optional and intended for replay workflows (verify-run, bisect, fast-replay).

using EpochSim;
using EpochSim.Kernel.Messaging;

var codec = Epoch.JsonCodecFromAssembly<Program>(t => t == typeof(Changed));
var serializer = Epoch.JsonStateSerializer<WorldState>();

using var run = Epoch.RecommendedRun(state, codec, serializer, rootDir: "artifacts");

[MessageKind("Changed")]
public sealed record Changed(int Delta) : IEvent;

RunTicks vs Session

Use RunTicks for batch jobs:

engine.RunTicks(state, seed: 1, endTickInclusive: 1000);

Use SimulationSession<TState> for long-lived loops (games, servers, interactive stepping):

var inbox = new CommandInbox();
engine.AttachInbox(inbox);

using var session = engine.CreateSession(state, seed: 1, startTick: 0);
inbox.Enqueue(new AddPopulation(5));
session.TickOnce();
session.RunUntil(100);

using EpochSim.Kernel.Messaging;
[MessageKind("AddPopulation")]
public sealed record AddPopulation(int Delta) : ICommand;

External Input Pattern (HTTP/UI/Queue -> Sim)

Use inboxes to feed external commands deterministically into the sim thread:

CommandInbox: commands for the next tick.
ScheduledCommandInbox: commands scheduled at a specific tick with stable ordering:
- primary key: tick ascending
- secondary key: insertion order

var scheduled = new ScheduledCommandInbox();
engine.AttachScheduledInbox(scheduled);

scheduled.Enqueue(10, new AddPopulation(3));
scheduled.Enqueue(10, new AddPopulation(7));
scheduled.Enqueue(12, new AddPopulation(1));

See full integration recipes: Embedding

CLI Onboarding

Create a starter app:

dotnet run --project src/EpochSim.Cli -- init .

Run and inspect artifacts:

dotnet run --project src/EpochSim.Cli -- run artifacts
dotnet run --project src/EpochSim.Cli -- list-runs artifacts
dotnet run --project src/EpochSim.Cli -- inspect-run artifacts <runId>

Determinism debugging:

dotnet run --project src/EpochSim.Cli -- verify-run artifacts <runId>
dotnet run --project src/EpochSim.Cli -- bisect artifacts <runId>

Samples

Recommended simple sample: src/EpochSim.Samples/Quickstart/QuickstartSample.cs
Advanced/legacy domain sample: src/EpochSim.Samples/Population/ (event-heavy diagnostic domain)

Build and Test

dotnet build EpochSim.slnx -m:1
dotnet test EpochSim.slnx -m:1

Docs

English:

Russian:

Echways/EpochSim.Executionv0.2.0

Get Started

Readme

EpochSim

State-Only Quickstart (No Events, No Codecs)

Recommended Artifacts

Event Log / Replay (Use When You Need Replay/Bisect)

RunTicks vs Session

External Input Pattern (HTTP/UI/Queue -> Sim)

CLI Onboarding

Samples

Build and Test

Docs

Echways/EpochSim.Executionv0.2.0

Get Started

Readme

EpochSim

State-Only Quickstart (No Events, No Codecs)

Recommended Artifacts

Event Log / Replay (Use When You Need Replay/Bisect)

RunTicks vs Session

External Input Pattern (HTTP/UI/Queue -> Sim)

CLI Onboarding

Samples

Build and Test

Docs