phanerozoic / threshold-hamming74encoder

threshold-hamming74encoder

Hamming(7,4) encoder. Transforms 4 data bits into a 7-bit codeword with single-error correction capability.

Circuit Overview

     d1  d2  d3  d4
      │   │   │   │
      ├───┼───┼───┤
      │   │   │   │
      │   │   │   └────────────────────────────► c7 = d4
      │   │   └───────────────────────► c6 = d3
      │   └──────────────────► c5 = d2
      └─────────────► c3 = d1
      │   │   │   │
      ▼   ▼   │   ▼
    ┌───────────────┐
    │ d1 XOR d2 XOR │──────► c1 = p1
    │      d4       │
    └───────────────┘
      │       │   │
      ▼       ▼   ▼
    ┌───────────────┐
    │ d1 XOR d3 XOR │──────► c2 = p2
    │      d4       │
    └───────────────┘
          │   │   │
          ▼   ▼   ▼
        ┌───────────────┐
        │ d2 XOR d3 XOR │──► c4 = p3
        │      d4       │
        └───────────────┘

The Hamming(7,4) Code

Richard Hamming invented this code in 1950. It encodes 4 data bits into 7 bits such that any single-bit error can be detected and corrected.

Codeword structure:

Parity equations:

• p1 = d1 ⊕ d2 ⊕ d4 (covers positions 1,3,5,7)
• p2 = d1 ⊕ d3 ⊕ d4 (covers positions 2,3,6,7)
• p3 = d2 ⊕ d3 ⊕ d4 (covers positions 4,5,6,7)

3-Way XOR Implementation

Each parity bit requires a 3-input XOR. In threshold logic:

XOR(a,b,c) = XOR(XOR(a,b), c)

      a   b
      │   │
      └─┬─┘
        ▼
    ┌───────┐
    │ XOR   │  (2 layers)
    └───────┘
        │
        │   c
        └─┬─┘
          ▼
      ┌───────┐
      │ XOR   │  (2 more layers)
      └───────┘
          │
          ▼
     XOR(a,b,c)

Total depth: 4 layers per parity. All three parities compute in parallel.

Code Properties

Example Encoding

Data: 1011

p1 = 1 ⊕ 0 ⊕ 1 = 0
p2 = 1 ⊕ 1 ⊕ 1 = 1
p3 = 0 ⊕ 1 ⊕ 1 = 0

Codeword: 0110011
          ↑↑ ↑
          p1p2p3

Architecture

Layers: 4 (two cascaded XOR stages)

All 16 Codewords

Note: Minimum Hamming distance between any two codewords is 3.

Usage

from safetensors.torch import load_file

w = load_file('model.safetensors')

def hamming74_encode(d1, d2, d3, d4):
    """Encode 4 data bits to 7-bit Hamming codeword"""
    # See model.py for full implementation
    pass

# Encode data word 1011
codeword = hamming74_encode(1, 0, 1, 1)
# Returns [0, 1, 1, 0, 0, 1, 1]

Files

threshold-hamming74encoder/
├── model.safetensors
├── model.py
├── config.json
└── README.md

License

MIT