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Fix mantissa underflow in block floating point quantization #21

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Fix mantissa underflow in block floating point quantization #21

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8 changes: 8 additions & 0 deletions src/num_sys_class.py
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Original file line number Diff line number Diff line change
Expand Up @@ -350,6 +350,10 @@ def quant_bfloat_py(self, float_arr, n_bits, n_exp):
power_exp_diff = torch.exp2(exp_diff)
mant_adj = mant / power_exp_diff

# handle mantissa underflow after shifting
# values that become subnormal should be clamped to maintain valid representation
mant_adj[mant_adj < 1.0] = 0.0

exp_adj = torch.full(exp.shape, shared_exp, device=float_arr.device)

# exp should not be larger than max_exp
Expand Down Expand Up @@ -415,6 +419,10 @@ def quant_bfloat_meta_py(self, float_arr, n_bits=8, n_exp=3):
power_exp_diff = torch.exp2(exp_diff)
mant_adj = mant / power_exp_diff

# handle mantissa underflow after shifting
# values that become subnormal should be clamped to maintain valid representation
mant_adj[mant_adj < 1.0] = 0.0

exp_adj = torch.full(exp.shape, shared_exp, device=float_arr.device)

# exp should not be larger than max_exp
Expand Down