threshold-mux4

4:1 multiplexer as threshold circuit. Selects one of four data inputs based on 2-bit select signal.

Circuit

d0 ──┐
d1 ──┼──► MUX4 ──► out
d2 ──┤      ▲
d3 ──┘      │
         s1 s0

Truth Table

s1	s0	out
0	0	d0
0	1	d1
1	0	d2
1	1	d3

Architecture

Layer	Neurons	Function
1	4	Select gates (one per input)
2	1	OR (combine selections)

Total: 5 neurons, 39 parameters, 2 layers

Each select gate fires only when:

1. Its data input is 1, AND
2. The select lines match its index

Usage

from safetensors.torch import load_file
import torch

w = load_file('model.safetensors')

def mux4(d0, d1, d2, d3, s1, s0):
    inp = torch.tensor([float(d0), float(d1), float(d2), float(d3),
                        float(s1), float(s0)])
    l1 = (inp @ w['layer1.weight'].T + w['layer1.bias'] >= 0).float()
    out = (l1 @ w['layer2.weight'].T + w['layer2.bias'] >= 0).float()
    return int(out.item())

Files

threshold-mux4/
├── model.safetensors
├── create_safetensors.py
├── config.json
└── README.md

License

MIT