Data Locality

Data Locality

One-line pattern summary

A performance-oriented pattern that places frequently accessed data in contiguous memory to improve cache efficiency.

Typical Unity use cases

• When updating a large number of objects such as bullets or particles every frame.
• When CPU bottlenecks need to be reduced.

Parts (roles)

• Hot Data: frequently accessed values
• Contiguous Storage: sequential arrays
• Loop: simple repetitive processing

Unity example (C#)

The code below is a simplified Unity example based on the scenario described above.

using UnityEngine;

public struct ProjectileState
{
    public Vector3 Position;
    public Vector3 Velocity;
}

public static class ProjectileSimulation
{
    public static void Simulate(ProjectileState[] projectileStates, float deltaTime)
    {
        for (int projectileIndex = 0; projectileIndex < projectileStates.Length; projectileIndex++)
        {
            projectileStates[projectileIndex].Position += projectileStates[projectileIndex].Velocity * deltaTime;
        }
    }
}

Advantages

• Sequential memory access reduces cache misses and improves throughput for large-scale calculations.
• It becomes especially powerful when combined with data-oriented systems such as Burst and Jobs.

Things to watch out for

• If the structure is optimized too heavily for performance, readability and domain clarity can suffer.
• Mistakes in array synchronization and index management can easily cause data mismatch bugs.

Interaction diagram

This shows the flow where contiguous memory blocks are processed sequentially to improve cache efficiency.