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"""
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Threshold Network for 2-Bit Ripple Carry Adder
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Adds two 2-bit numbers with carry in, producing 2-bit sum and carry out.
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Built from two cascaded full adders.
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"""
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import torch
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from safetensors.torch import load_file
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def heaviside(x):
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return (x >= 0).float()
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class ThresholdRippleCarry2Bit:
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"""
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2-bit ripple carry adder: (a1,a0) + (b1,b0) + cin = (cout, s1, s0)
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"""
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def __init__(self, weights_dict):
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self.weights = weights_dict
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def half_adder(self, prefix, a, b):
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inputs = torch.tensor([float(a), float(b)])
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or_out = heaviside((inputs * self.weights[f'{prefix}.sum.layer1.or.weight']).sum() +
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self.weights[f'{prefix}.sum.layer1.or.bias'])
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nand_out = heaviside((inputs * self.weights[f'{prefix}.sum.layer1.nand.weight']).sum() +
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self.weights[f'{prefix}.sum.layer1.nand.bias'])
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layer1 = torch.tensor([or_out, nand_out])
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sum_out = heaviside((layer1 * self.weights[f'{prefix}.sum.layer2.weight']).sum() +
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self.weights[f'{prefix}.sum.layer2.bias'])
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carry_out = heaviside((inputs * self.weights[f'{prefix}.carry.weight']).sum() +
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self.weights[f'{prefix}.carry.bias'])
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return int(sum_out.item()), int(carry_out.item())
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def full_adder(self, prefix, a, b, cin):
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s1, c1 = self.half_adder(f'{prefix}.ha1', a, b)
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sum_out, c2 = self.half_adder(f'{prefix}.ha2', s1, cin)
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carry_inputs = torch.tensor([float(c1), float(c2)])
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cout = heaviside((carry_inputs * self.weights[f'{prefix}.carry_or.weight']).sum() +
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self.weights[f'{prefix}.carry_or.bias'])
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return int(sum_out), int(cout.item())
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def __call__(self, a0, a1, b0, b1, cin=0):
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s0, c0 = self.full_adder('fa0', a0, b0, cin)
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s1, cout = self.full_adder('fa1', a1, b1, c0)
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return s0, s1, cout
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@classmethod
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def from_safetensors(cls, path="model.safetensors"):
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return cls(load_file(path))
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if __name__ == "__main__":
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model = ThresholdRippleCarry2Bit.from_safetensors("model.safetensors")
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print("2-Bit Ripple Carry Adder Tests:")
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print("-" * 50)
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for a in range(4):
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for b in range(4):
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a0, a1 = a & 1, (a >> 1) & 1
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b0, b1 = b & 1, (b >> 1) & 1
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s0, s1, cout = model(a0, a1, b0, b1, 0)
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result = s0 + 2*s1 + 4*cout
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expected = a + b
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status = "OK" if result == expected else "FAIL"
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print(f"{a} + {b} = {result} (s1s0={s1}{s0}, cout={cout}) [{status}]")
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