68 lines
2.4 KiB
Python
68 lines
2.4 KiB
Python
import torch
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def calc_mantissa(abs_x, exponent, normal_mask, MANTISSA_BITS, EXPONENT_BIAS, generator=None):
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mantissa_scaled = torch.where(
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normal_mask,
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(abs_x / (2.0 ** (exponent - EXPONENT_BIAS)) - 1.0) * (2**MANTISSA_BITS),
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(abs_x / (2.0 ** (-EXPONENT_BIAS + 1 - MANTISSA_BITS)))
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)
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mantissa_scaled += torch.rand(mantissa_scaled.size(), dtype=mantissa_scaled.dtype, layout=mantissa_scaled.layout, device=mantissa_scaled.device, generator=generator)
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return mantissa_scaled.floor() / (2**MANTISSA_BITS)
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#Not 100% sure about this
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def manual_stochastic_round_to_float8(x, dtype, generator=None):
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if dtype == torch.float8_e4m3fn:
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EXPONENT_BITS, MANTISSA_BITS, EXPONENT_BIAS = 4, 3, 7
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elif dtype == torch.float8_e5m2:
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EXPONENT_BITS, MANTISSA_BITS, EXPONENT_BIAS = 5, 2, 15
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else:
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raise ValueError("Unsupported dtype")
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x = x.half()
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sign = torch.sign(x)
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abs_x = x.abs()
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sign = torch.where(abs_x == 0, 0, sign)
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# Combine exponent calculation and clamping
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exponent = torch.clamp(
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torch.floor(torch.log2(abs_x)) + EXPONENT_BIAS,
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0, 2**EXPONENT_BITS - 1
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)
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# Combine mantissa calculation and rounding
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normal_mask = ~(exponent == 0)
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abs_x[:] = calc_mantissa(abs_x, exponent, normal_mask, MANTISSA_BITS, EXPONENT_BIAS, generator=generator)
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sign *= torch.where(
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normal_mask,
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(2.0 ** (exponent - EXPONENT_BIAS)) * (1.0 + abs_x),
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(2.0 ** (-EXPONENT_BIAS + 1)) * abs_x
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)
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inf = torch.finfo(dtype)
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torch.clamp(sign, min=inf.min, max=inf.max, out=sign)
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return sign
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def stochastic_rounding(value, dtype, seed=0):
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if dtype == torch.float32:
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return value.to(dtype=torch.float32)
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if dtype == torch.float16:
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return value.to(dtype=torch.float16)
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if dtype == torch.bfloat16:
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return value.to(dtype=torch.bfloat16)
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if dtype == torch.float8_e4m3fn or dtype == torch.float8_e5m2:
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generator = torch.Generator(device=value.device)
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generator.manual_seed(seed)
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output = torch.empty_like(value, dtype=dtype)
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num_slices = max(1, (value.numel() / (4096 * 4096)))
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slice_size = max(1, round(value.shape[0] / num_slices))
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for i in range(0, value.shape[0], slice_size):
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output[i:i+slice_size].copy_(manual_stochastic_round_to_float8(value[i:i+slice_size], dtype, generator=generator))
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return output
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return value.to(dtype=dtype)
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