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

# threshold-iszero4

4-bit zero detector. Outputs 1 if all 4 input bits are zero.

## Function

iszero4(a, b, c, d) = 1 if (a + b + c + d) == 0, else 0

Equivalent to 4-input NOR gate.

## Architecture

Single neuron: weights [-1, -1, -1, -1], bias 0

Fires when: -a - b - c - d + 0 >= 0, i.e., all inputs are 0.

## Parameters

| | |
|---|---|
| Inputs | 4 |
| Outputs | 1 |
| Neurons | 1 |
| Layers | 1 |
| Parameters | 5 |
| Magnitude | 4 |

## Usage

```python
from safetensors.torch import load_file
import torch

w = load_file('model.safetensors')

def iszero4(a, b, c, d):
    inp = torch.tensor([float(a), float(b), float(c), float(d)])
    return int((inp @ w['neuron.weight'].T + w['neuron.bias'] >= 0).item())

print(iszero4(0, 0, 0, 0))  # 1 (is zero)
print(iszero4(0, 0, 0, 1))  # 0 (not zero)
```

## License

MIT