Could you provide more details about the RMR(Reporter-Manager-Receiver) model?

[sfireworks]

Thanks for sharing this work. In your document , i noticed the design pattern is DOP, and the modified ECS pattern - RMR is used in the implementation of libuipc. I am curious about the RMR pattern, but when i go through the papers and documents, i could not find any related information about RMR, could you provides more design details of RMR, such as how is RMR different from ECS， and what's advantage could RMR provide?

[MuGdxy]

GOOD question! The RMR pattern documentation is currently limited. We'll gradually improve the documentation to make these design decisions more transparent. Here's a brief answer to help clarify the concept:

Understanding the RMR (Reporter-Manager-Receiver) Pattern

RMR is a modified ECS pattern designed for cache-friendly physics simulation. Here's how it works:

The Three Roles

1. Reporter (Data Producer)

• Self-register with the Manager during build phase
• Report how much data they'll produce
• Generate data (e.g., contact forces, friction)
• Write data into pre-allocated buffer slices assigned by the Manager

2. Manager (Central Coordinator)

• Collects all reporter registrations
• Allocates ONE large contiguous buffer for all reporters
• Assigns each reporter a non-overlapping memory slice (via offset scanning)
• Processes/sorts the collected data
• Optionally distributes filtered data to receivers

3. Receiver (Data Consumer) - Optional

• Subsystems that need processed data (e.g., Newton solver)
• Specify what data subset they need (e.g., "gradients for vertices 100-200")
• Receive only their requested filtered data

Typical Flow

REPORTER: 
     1. NormalContactReporter → buffer[0...150]
     2. FrictionalContactReporter → buffer[150...400]

MANAGER: 
     1. Query extents → [150, 250]
     2. Scan offsets → [0, 150]
     3. Allocate contiguous buffer[400]
     4. Reporters fill their slices
     5. Sort/convert to efficient format
     6. (Optional) Distribute to receivers

RECEIVERS: (Optional) Request filtered data -> receive only what they need
    1. Affine Body Related Contact
    2. Finite Element Related Contact

Why RMR Works for Simulation

Simulation problems are mathematically well-defined. The abstraction comes from the mathematical formulation first, not from software engineering patterns. The quality of a simulation framework depends primarily on its mathematical design - how properly it models PDEs, constraints, and physical laws.

Because the problem is already abstracted at the mathematical level (forces, energies, gradients, Hessians), we don't need additional conceptual abstractions from OOP. Instead, we can focus on data-oriented design that matches the mathematical structure: collect contributions from various sources, aggregate them efficiently, and solve the system. RMR naturally fits this mathematical workflow.

How RMR Differs from Traditional ECS

Traditional ECS	RMR Pattern
Component arrays per type	Single contiguous buffer for all reporters
Systems pull data from components	Reporters push → Manager → (optionally) Receivers pull
Potential access conflicts	Phase-separated (write → process → read)
Memory fragmentation	Contiguous allocation via offset scanning

Key Advantages

1. Cache-friendly: All data in one contiguous buffer
2. GPU-friendly: Contiguous buffers, offset-based indexing
3. Flexible: Receivers get only the data they request (when used)
4. Safe: Manager controls all data flow phases
5. Subsystem Unawareness: Each reporter maintains its own private, implementation-specific data structures internally. The manager provides a common data structure interface that all reporters output to. Reporters can have completely different internal representations, but they all write to the same standardized output format. The manager doesn't know or care about reporter internals - it only provides the common data buffers.