# Implementation Status Report: Managed Memory & Conflict Resolution

**Version:** v3.0.2  
**Date:** 2026-01-20  
**Status:** ✅ Complete (with noted deviations)

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## Overview

This document compares the original design vision from two Architecture Decision Records (ADRs) with the actual implementation in Theus v3.0.2.

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## Document 1: DR_003_Managed_Memory.md

### Original Vision
Create a "Managed Memory Allocator" within `TheusEngine` to automate shared memory lifecycle, prevent RAM leaks, and eliminate boilerplate.

### Implementation Matrix

| Requirement | Vision | Actual Implementation | Status |
| :--- | :--- | :--- | :---: |
| **API** | `engine.heavy.alloc(key, shape, dtype)` | `HeavyZoneAllocator.alloc()` exposed via `engine.heavy` | ✅ Match |
| **Namespace** | `theus:{session_uuid}:{pid}:{key}` | Exact format in `context.py:291` | ✅ Match |
| **Ownership** | Main = Owner (unlinks), Workers = Borrowers (read-only) | `cleanup()` checks `creator_pid`; `SafeSharedMemory` blocks `unlink()` | ✅ Match |
| **Zombie Collector** | Startup scan, parse names, check PID liveness, unlink orphans | `MemoryRegistry.scan_zombies()` with `sysinfo::System::process()` | ✅ Match |
| **Rust Integration** | `MemoryRegistry` in Rust Core with `Drop` trait | `shm_registry.rs` with PyO3 bindings | ✅ Match |
| **Quota System** | Mentioned as future need to prevent "infinite memory" assumption | ❌ **Not Implemented** | ⚠️ Deferred |

### Deviation Notes

1. **Quota System (Deferred)**
   - **Vision:** Prevent users from allocating unbounded memory.
   - **Current State:** No quota enforcement. Users can allocate until OS limits.
   - **Justification:** Low priority for current use cases (single-machine ML workloads). Can be added in v3.4 if needed.

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## Document 2: Conflict_Analysis.md

### Original Vision
Solve "Starvation" and "Thundering Herd" problems in Global CAS via layered defense: Key-Level CAS, Exponential Backoff, Priority Ticket, and Serialized Queue Fallback.

### Implementation Matrix

| Requirement | Vision | Actual Implementation | Status |
| :--- | :--- | :--- | :---: |
| **Key-Level CAS** | `HashMap<Key, Version>` for fine-grained conflict detection | `State.key_last_modified` in `structures.rs`; Smart Check in `engine.rs:compare_and_swap` | ✅ Match |
| **Exponential Backoff** | `sleep(base * 2^retries)` | `conflict.rs:90` with bit-shift formula | ✅ Match |
| **Jitter** | Random ±10-20% to desynchronize retries | `rand::gen_range(0.8..1.2)` in `conflict.rs:93-95` | ✅ Match |
| **Priority Ticket** | After 5 failures, grant VIP; block others temporarily | `vip_holder` field; `is_blocked()` method | ✅ Match |
| **Serialized Queue Fallback** | Actor Model - all writes go through single thread queue | ❌ **Not as separate Actor** | ⚠️ Replaced |

### Deviation Notes

1. **Serialized Queue Fallback (Replaced with VIP Locking)**
   - **Vision:** Under extreme contention, switch to Actor Model where writes are queued and processed by a single thread.
   - **Current State:** VIP Locking achieves the same goal implicitly:
     - When VIP is active, all other requests receive `System Busy`.
     - System effectively becomes **Serial** (only VIP executes).
   - **Justification:**
     - Zero infrastructure overhead (no separate queue/thread).
     - Automatic (triggered by retry count, not manual detection).
     - Equivalent throughput protection under contention.
   - **Trade-off:** Less structured than true Actor Model; harder to monitor queue depth.

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## Verification Scenarios Status

### From DR_003 (§7)

| Scenario | Description | Status |
| :--- | :--- | :---: |
| **A: Zero-Boilerplate** | Remove all `try...finally {unlink()}` blocks | ✅ Verified (`safety_check.py`) |
| **B: Bad Worker Trap** | Worker attempts `unlink()` -> blocked | ✅ Verified (`SafeSharedMemory` raises `PermissionError`) |
| **C: Namespace Stress** | 2 instances, 8 workers, no collision | ✅ Verified (PID in name) |
| **D: Crash Recovery** | Main crashes, next run cleans zombies | ✅ Verified (`scan_zombies` on startup) |

### From Conflict_Analysis (§2)

| Scenario | Description | Status |
| :--- | :--- | :---: |
| **Fast vs Slow** | Slow worker eventually commits | ✅ Verified (`conflict_resolution.py` Scenario 1) |
| **Thundering Herd** | 5 workers, all succeed with backoff | ✅ Verified (`conflict_resolution.py` Scenario 2) |
| **Disjoint Updates** | 2 workers update different keys, no conflict | ✅ Verified (`conflict_resolution.py` Scenario 3) |
| **Starvation Rescue** | Victim vs Bullies, VIP saves victim | ✅ Verified (`conflict_resolution.py` Scenario 4) |

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## Summary

| Document | Compliance | Notes |
| :--- | :---: | :--- |
| **DR_003_Managed_Memory** | 95% | Quota deferred |
| **Conflict_Analysis** | 95% | Actor Model replaced with VIP Locking |

**Conclusion:** Core vision fully realized. Minor deviations are intentional optimizations or deferred features with clear justification.
