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---

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


# threshold-mod4

Computes Hamming weight mod 4 directly on inputs. Single-layer circuit using repeated weight pattern.

## 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”‚

   w: 1  1  1 -3  1  1  1 -3

   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”‚ b:  0   β”‚

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

               β”‚

               β–Ό

           HW mod 4

```

## Algebraic Insight

The pattern `(1, 1, 1, -3)` repeats twice across 8 inputs:

- Positions 1-3: weight +1 each
- Position 4: weight -3 (reset: 1+1+1-3 = 0)
- Positions 5-7: weight +1 each
- Position 8: weight -3 (reset again)

Every 4 bits, the sum resets. For 8 bits, two complete cycles.

```

HW=0: sum=0 β†’ 0 mod 4

HW=1: sum=1 β†’ 1 mod 4

HW=2: sum=2 β†’ 2 mod 4

HW=3: sum=3 β†’ 3 mod 4

HW=4: sum=0 β†’ 0 mod 4  (reset)

...

```

## Parameters

| | |
|---|---|
| Weights | [1, 1, 1, -3, 1, 1, 1, -3] |
| Bias | 0 |
| Total | 9 parameters |

## MOD-m Family

| m | Weight pattern |
|---|----------------|
| 3 | (1, 1, -2) |
| **4** | **(1, 1, 1, -3)** |
| 5 | (1, 1, 1, 1, -4) |
| m | (1, ..., 1, 1-m) with m-1 ones |

## Usage

```python

from safetensors.torch import load_file

import torch



w = load_file('model.safetensors')



def mod4(bits):

    inputs = torch.tensor([float(b) for b in bits])

    return int((inputs * w['weight']).sum() + w['bias'])

```

## Files

```

threshold-mod4/

β”œβ”€β”€ model.safetensors

β”œβ”€β”€ model.py

β”œβ”€β”€ config.json

└── README.md

```

## License

MIT