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--- |
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license: mit |
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tags: |
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- pytorch |
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- safetensors |
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- threshold-logic |
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- neuromorphic |
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- arithmetic |
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--- |
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# threshold-subtractor4bit |
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4-bit subtractor. Computes A - B (modulo 16) with borrow output. |
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## Function |
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subtractor4bit(A, B) = (A - B) mod 16, borrow_out |
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## Truth Table (selected rows) |
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| A | B | Diff | Borrow | |
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|---|---|------|--------| |
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| 7 | 3 | 4 | 0 | |
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| 5 | 5 | 0 | 0 | |
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| 3 | 7 | 12 | 1 | |
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| 0 | 1 | 15 | 1 | |
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## Architecture |
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Ripple-borrow subtractor using full subtractor units. |
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For each bit i: |
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- diff_i = a_i XOR b_i XOR borrow_{i-1} |
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- borrow_i = majority(NOT(a_i), b_i, borrow_{i-1}) |
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The borrow signal indicates A < B (unsigned comparison). |
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## Parameters |
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|---|---| |
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| Inputs | 8 (a3-a0, b3-b0) | |
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| Outputs | 5 (d3-d0, bout) | |
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| Neurons | 25 | |
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| Layers | 8 | |
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| Parameters | 86 | |
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| Magnitude | 88 | |
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## Usage |
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```python |
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from safetensors.torch import load_file |
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# See model.py for full implementation |
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# 7 - 3 = 4 |
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# subtractor4(0,1,1,1, 0,0,1,1) = [0,1,0,0, 0] |
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# 3 - 7 = 12 (wraps), borrow=1 |
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# subtractor4(0,0,1,1, 0,1,1,1) = [1,1,0,0, 1] |
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``` |
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## License |
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MIT |
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