44 lines
1.3 KiB
Python
44 lines
1.3 KiB
Python
import torch
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def fp8_quantize(weight, qdtype=torch.float8_e4m3fn):
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device = weight.device
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# weight, scale = quant_weights(weight, torch.int8, False)
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finfo = torch.finfo(qdtype)
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# Calculate the scale as dtype max divided by absmax
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scale = finfo.max / weight.abs().max().clamp(min=1e-12)
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# scale and clamp the tensor to bring it to
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# the representative range of float8 data type
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# (as default cast is unsaturated)
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qweight = (weight * scale).clamp(min=finfo.min, max=finfo.max)
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# Return both float8 data and the inverse scale (as float),
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# as both required as inputs to torch._scaled_mm
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qweight = qweight.to(qdtype)
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scale = scale.float().reciprocal()
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return qweight, scale
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class Fp8Linear(torch.nn.Module):
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def __init__(
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self,
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weight,
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bias,
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) -> None:
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super().__init__()
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self.dtype = weight.dtype
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self.qweight, self.scale = fp8_quantize(weight)
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self.bias = bias if bias is not None else None
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def forward(self, input: torch.Tensor) -> torch.Tensor:
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qinput, scale = fp8_quantize(input)
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output, _ = torch._scaled_mm(
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qinput,
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self.qweight.t(),
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out_dtype=self.dtype,
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scale_a=scale,
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scale_b=self.scale,
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bias=self.bias,
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)
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return output
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