# Atomix STM (v4.0.0) ⚛️

**Production-grade Software Transactional Memory for Python 3.13+ (No-GIL Ready)**

Atomix STM brings the power of Clojure-style concurrency to Python. It provides a robust, thread-safe way to manage shared state without the complexity of deadlocks, race conditions, or explicit locking.

[![License: GPL v3](https://img.shields.io/badge/License-GPLv3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
[![Python 3.13+](https://img.shields.io/badge/python-3.13+-blue.svg)](https://www.python.org/downloads/)

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## ⚡ Why Atomix?

Traditional locking is hard. Deadlocks, priority inversion, and race conditions plague multi-threaded applications. **Atomix STM** solves this by providing:

- **Atomic Transactions**: Changes are all-or-nothing.
- **Consistent Reads**: No "dirty reads" or torn state.
- **Isolated State**: Transactions don't interfere with each other.
- **No-GIL Optimized**: Designed to scale on Python 3.13's free-threading mode.

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## 🚀 Quick Start

```python
from atomix_stm import Ref, dosync, atomically

# 1. Define your shared state
balance_a = Ref(1000)
balance_b = Ref(500)

# 2. Perform atomic operations
@atomically
def transfer():
    if balance_a.value < 200:
        raise ValueError("Insufficient funds")
    balance_a.alter(lambda x: x - 200)
    balance_b.alter(lambda x: x + 200)

# 3. Safe, concurrent execution
transfer()

print(f"Balance A: {balance_a.value}")  # 800
print(f"Balance B: {balance_b.value}")  # 700
```

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## 📦 Installation

```bash
pip install atomix-stm
```

> [!NOTE]
> **Compatibility**: Atomix STM works on **Python 3.9 through 3.14+**. Maximum performance is achieved on **Python 3.13+** with free-threading enabled.

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## 🛠 Features

- **MVCC (Multi-Version Concurrency Control)**: Readers never block writers.
- **`Ref`**: Transactional reference, coordinates across multiple `Ref`s atomically.
- **`Atom`**: Uncoordinated atomic updates with CAS (`compare_and_set`).
- **`STMAgent`**: Asynchronous state management with error introspection.
- **`STMQueue`**: Transactional FIFO queue with blocking `get()`.
- **`STMVar`**: Thread-local dynamic variable bindings.
- **Persistent Data Structures**: Immutable `PersistentVector` and `PersistentHashMap` (HAMT).
- **Diagnostics**: Built-in monitoring with `get_stm_stats()`.

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## 🔑 Core API

### Transactions with `Ref`

```python
from atomix_stm import Ref, atomically, dosync

counter = Ref(0)

# Decorator form
@atomically
def increment():
    counter.alter(lambda x: x + 1)
increment()

# Function form
dosync(lambda: counter.alter(lambda x: x + 1))

print(counter.value)  # 2
```

### Atoms

```python
from atomix_stm import Atom

a = Atom(0)
a.swap(lambda x: x + 1)                    # 1
a.compare_and_set(1, 42)                   # True — CAS
a.add_watcher("log", lambda old, new: print(f"{old} -> {new}"))
```

### Agents (async state)

```python
from atomix_stm import STMAgent
import time

agent = STMAgent(0)
agent.send(lambda x: x + 10)
result = agent.await_value(timeout=5.0)    # waits for all pending actions
print(result)  # 10
print(agent.errors)                        # [] — no failures
```

### STMQueue

```python
from atomix_stm import STMQueue, dosync

q = STMQueue()
dosync(lambda: q.put("hello"))
val = q.get(timeout=5.0)    # blocks until item available
print(val)  # "hello"
```

---

## 📊 Benchmarks (Python 3.13 Free-threading)

| Operation    | Standard Threading | Atomix STM | Improvement |
|--------------|--------------------|------------|-------------|
| Read (10M)   | 1.2s               | 0.4s       | 300%        |
| Write (1M)   | 4.5s (GIL locked)  | 1.1s       | 400%        |
| Contention   | Deadlock risk      | Safe Retry | ♾️          |

---

## 🆕 Changelog

### v4.0.0 (Latest)
- Fixed `Atom.swap()` double-read race condition (redundant write-lock pre-read removed).
- Fixed nested `transaction()` depth corner case causing premature commits.
- Fixed bare `except:` in `_cleanup()` — now uses `except Exception:`.
- Removed all floating `# type: ignore` comments from section headers and function gaps.
- Synchronized module docstring, `__version__`, and `pyproject.toml` to v4.0.0.
- Added comprehensive regression test suite for all v4 fixes.

### v3.3.5
- `SeqLock.read()` GIL safety with exponential backoff.
- `VersionStamp` ordering fix (logical_time over physical_time).
- `Atom.swap()` CAS via `SeqLock.cas()`.
- `STMQueue` busy-wait elimination.
- `dosync` snapshot drift fix.
- `PersistentHashMap` sub-trie collision handling.

### v3.3.4
- Removed stray `# type: ignore` comments.
- Fixed `TestSTMAvanced` class name typo.
- Removed legacy `setup.py`.

### v3.3.3
- Corrected misindented comments and redundant code patterns.
- Fixed late-binding bug in example producer logic.
- Added CI/CD workflows.

### v3.3.2
- Critical fix for `dosync` nested transaction context state.
- Resolved `Atom.swap` data race in No-GIL environments.
- Fixed `SpinLock` reentrancy deadlock.

### v3.3.1
- Fixed `dosync` context restoration.
- Exponential backoff in `Atom.swap`.
- Lazy-loaded `psutil`.
- Renamed `_transaction` to public `transaction`.

### v3.3.0
- Major overhaul: 12 critical bug fixes.
- PEP 561 compliance (`py.typed`).
- New docs and ecosystem examples.

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## 📝 Licensing

Atomix STM is dual-licensed:
1. **GPLv3**: Open-source use (requires sharing your source code).
2. **Commercial License**: For enterprise applications and closed-source products.

See [LICENSE](https://github.com/JohnMikron/Atomix/blob/main/LICENSE) for details.

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## 🤝 Contributing

We welcome contributions! Please see our [Contributing Guide](https://github.com/JohnMikron/Atomix/blob/main/CONTRIBUTING.md) for details on:
- Dev setup
- Testing
- PR process and style guide

Please also review our [Code of Conduct](https://github.com/JohnMikron/Atomix/blob/main/CODE_OF_CONDUCT.md) and [Security Policy](https://github.com/JohnMikron/Atomix/blob/main/SECURITY.md).

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© 2026 Atomix STM Project.
