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---

license: mit
tags:
- pytorch
- safetensors
- threshold-logic
- neuromorphic
- modular-arithmetic
---


# threshold-mod5

Computes Hamming weight mod 5 for 8-bit inputs. Multi-layer network with thermometer encoding.

## Circuit

```

  xβ‚€ x₁ xβ‚‚ x₃ xβ‚„ xβ‚… x₆ x₇

   β”‚  β”‚  β”‚  β”‚  β”‚  β”‚  β”‚  β”‚

   β””β”€β”€β”΄β”€β”€β”΄β”€β”€β”΄β”€β”€β”Όβ”€β”€β”΄β”€β”€β”΄β”€β”€β”΄β”€β”€β”˜

               β–Ό

       β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”

       β”‚ Thermometer β”‚  Layer 1: 9 neurons

       β”‚  Encoding   β”‚

       β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜

               β”‚

               β–Ό

       β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”

       β”‚  MOD-5      β”‚  Layer 2: 4 neurons

       β”‚  Detection  β”‚  Pattern (1,1,1,1,-4)

       β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜

               β”‚

               β–Ό

       β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”

       β”‚  Classify   β”‚  Output: 5 classes

       β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜

               β”‚

               β–Ό

        {0, 1, 2, 3, 4}

```

## Algebraic Insight

Pattern `(1, 1, 1, 1, -4)` causes cumulative sums to cycle mod 5:

```

HW=0: sum=0 β†’ 0 mod 5

HW=1: sum=1 β†’ 1 mod 5

HW=2: sum=2 β†’ 2 mod 5

HW=3: sum=3 β†’ 3 mod 5

HW=4: sum=4 β†’ 4 mod 5

HW=5: sum=0 β†’ 0 mod 5  (reset: 1+1+1+1-4=0)

HW=6: sum=1 β†’ 1 mod 5

HW=7: sum=2 β†’ 2 mod 5

HW=8: sum=3 β†’ 3 mod 5

```

## Architecture

| Layer | Neurons | Function |
|-------|---------|----------|
| Input | 8 | Binary bits |
| Hidden 1 | 9 | Thermometer encoding |
| Hidden 2 | 4 | MOD-5 detection |
| Output | 5 | One-hot classification |

**Total: 18 neurons, 146 parameters**

## Output Distribution

| Class | HW values | Count/256 |
|-------|-----------|-----------|
| 0 | 0, 5 | 57 |
| 1 | 1, 6 | 36 |
| 2 | 2, 7 | 36 |
| 3 | 3, 8 | 57 |
| 4 | 4 | 70 |

## Usage

```python

from safetensors.torch import load_file

import torch



w = load_file('model.safetensors')



def forward(x):

    x = x.float()

    x = (x @ w['layer1.weight'].T + w['layer1.bias'] >= 0).float()

    x = (x @ w['layer2.weight'].T + w['layer2.bias'] >= 0).float()

    out = x @ w['output.weight'].T + w['output.bias']

    return out.argmax(dim=-1)

```

## Files

```

threshold-mod5/

β”œβ”€β”€ model.safetensors

β”œβ”€β”€ model.py

β”œβ”€β”€ config.json

└── README.md

```

## License

MIT