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import os
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import torch
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import torch.nn as nn
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from torch.nn import functional as F
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def get_fp_maxval(bits=8, mantissa_bit=3, sign_bits=1):
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_bits = torch.tensor(bits)
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_mantissa_bit = torch.tensor(mantissa_bit)
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_sign_bits = torch.tensor(sign_bits)
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M = torch.clamp(torch.round(_mantissa_bit), 1, _bits - _sign_bits)
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E = _bits - _sign_bits - M
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bias = 2 ** (E - 1) - 1
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mantissa = 1
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for i in range(mantissa_bit - 1):
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mantissa += 1 / (2 ** (i+1))
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maxval = mantissa * 2 ** (2**E - 1 - bias)
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return maxval
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def quantize_to_fp8(x, bits=8, mantissa_bit=3, sign_bits=1):
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"""
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Default is E4M3.
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"""
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bits = torch.tensor(bits)
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mantissa_bit = torch.tensor(mantissa_bit)
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sign_bits = torch.tensor(sign_bits)
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M = torch.clamp(torch.round(mantissa_bit), 1, bits - sign_bits)
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E = bits - sign_bits - M
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bias = 2 ** (E - 1) - 1
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mantissa = 1
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for i in range(mantissa_bit - 1):
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mantissa += 1 / (2 ** (i+1))
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maxval = mantissa * 2 ** (2**E - 1 - bias)
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minval = - maxval
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minval = - maxval if sign_bits == 1 else torch.zeros_like(maxval)
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input_clamp = torch.min(torch.max(x, minval), maxval)
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log_scales = torch.clamp((torch.floor(torch.log2(torch.abs(input_clamp)) + bias)).detach(), 1.0)
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log_scales = 2.0 ** (log_scales - M - bias.type(x.dtype))
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qdq_out = torch.round(input_clamp / log_scales) * log_scales
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return qdq_out, log_scales
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def fp8_tensor_quant(x, scale, bits=8, mantissa_bit=3, sign_bits=1):
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for i in range(len(x.shape) - 1):
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scale = scale.unsqueeze(-1)
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new_x = x / scale
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quant_dequant_x, log_scales = quantize_to_fp8(new_x, bits=bits, mantissa_bit=mantissa_bit, sign_bits=sign_bits)
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return quant_dequant_x, scale, log_scales
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def fp8_activation_dequant(qdq_out, scale, dtype):
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qdq_out = qdq_out.type(dtype)
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quant_dequant_x = qdq_out * scale.to(dtype)
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return quant_dequant_x
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def fp8_linear_forward(cls, original_dtype, input):
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weight_dtype = cls.weight.dtype
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if cls.weight.dtype != torch.float8_e4m3fn:
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maxval = get_fp_maxval()
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scale = torch.max(torch.abs(cls.weight.flatten())) / maxval
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linear_weight, scale, log_scales = fp8_tensor_quant(cls.weight, scale)
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linear_weight = linear_weight.to(torch.float8_e4m3fn)
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weight_dtype = linear_weight.dtype
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else:
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scale = cls.fp8_scale.to(cls.weight.device)
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linear_weight = cls.weight
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if weight_dtype == torch.float8_e4m3fn and cls.weight.sum() != 0:
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if True or len(input.shape) == 3:
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cls_dequant = fp8_activation_dequant(linear_weight, scale, original_dtype)
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if cls.bias != None:
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output = F.linear(input, cls_dequant, cls.bias)
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else:
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output = F.linear(input, cls_dequant)
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return output
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else:
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return cls.original_forward(input.to(original_dtype))
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else:
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return cls.original_forward(input)
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def convert_fp8_linear(module, dit_weight_path, original_dtype, params_to_keep={}):
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setattr(module, "fp8_matmul_enabled", True)
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fp8_map_path = dit_weight_path.replace('.pt', '_map.pt')
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if os.path.exists(fp8_map_path):
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fp8_map = torch.load(fp8_map_path, map_location=lambda storage, loc: storage)
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else:
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raise ValueError(f"Invalid fp8_map path: {fp8_map_path}.")
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fp8_layers = []
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for key, layer in module.named_modules():
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if isinstance(layer, nn.Linear) and ('double_blocks' in key or 'single_blocks' in key):
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fp8_layers.append(key)
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original_forward = layer.forward
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layer.weight = torch.nn.Parameter(layer.weight.to(torch.float8_e4m3fn))
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setattr(layer, "fp8_scale", fp8_map[key].to(dtype=original_dtype))
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setattr(layer, "original_forward", original_forward)
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setattr(layer, "forward", lambda input, m=layer: fp8_linear_forward(m, original_dtype, input))
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