threshold-signbit4 / README.md
CharlesCNorton
Extract sign bit of 4-bit number, magnitude 2
ccee2d3
metadata
license: mit
tags:
  - pytorch
  - safetensors
  - threshold-logic
  - neuromorphic

threshold-signbit4

Extract sign bit (MSB) of 4-bit number.

Function

signbit4(a3, a2, a1, a0) = a3

In 2's complement representation:

  • Output 0: non-negative (0 to 7)
  • Output 1: negative (-8 to -1)

Truth Table

a3 a2 a1 a0 unsigned signed signbit
0 0 0 0 0 0 0
0 1 1 1 7 +7 0
1 0 0 0 8 -8 1
1 1 1 1 15 -1 1

Architecture

Single neuron extracting MSB:

  • Weights: [1, 0, 0, 0]
  • Bias: -1

Fires when: a3 - 1 >= 0, i.e., a3 >= 1

Parameters

Inputs 4
Outputs 1
Neurons 1
Layers 1
Parameters 5
Magnitude 2

Usage

from safetensors.torch import load_file
import torch

w = load_file('model.safetensors')

def signbit4(a3, a2, a1, a0):
    inp = torch.tensor([float(a3), float(a2), float(a1), float(a0)])
    return int((inp @ w['neuron.weight'].T + w['neuron.bias'] >= 0).item())

print(signbit4(0, 1, 1, 1))  # 0 (value = +7)
print(signbit4(1, 0, 0, 0))  # 1 (value = -8)

License

MIT