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Add bitsandbytes fp4 support #7320

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Add bitsandbytes fp4 support #7320

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27 changes: 12 additions & 15 deletions vllm/model_executor/model_loader/loader.py
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Original file line number Diff line number Diff line change
Expand Up @@ -812,13 +812,12 @@ def quantized_checkpoint() -> Generator:
for weight_name, weight_tensor in weight_iterator:
if weight_name.endswith(".weight"):
continue
# TODO: only nf4 quantization is supported for now
if weight_name.endswith(".quant_state.bitsandbytes__fp4"):
raise NotImplementedError(
"Only bitsandbytes_nf4 quantization"
f"is supported for now. {weight_name} is fp4 quantized"
)
temp_state_dict[weight_name] = weight_tensor
# bitsandbytes library requires
# weight.quant_state.bitsandbytes__* in CPU
if "quant_state.bitsandbytes" in weight_name:
temp_state_dict[weight_name] = weight_tensor.cpu().data
else:
temp_state_dict[weight_name] = weight_tensor

# Closure to parse quant_state for each prequant weight
def _parse_quant_state(param_name: str,
Expand All @@ -827,12 +826,6 @@ def _parse_quant_state(param_name: str,
for k in temp_state_dict:
if param_name + "." in k:
quant_state[k] = temp_state_dict[k]
# bitsandbytes library requires
# weight.quant_state.bitsandbytes__nf4 in CPU
quant_state[param_name +
".quant_state.bitsandbytes__nf4"] = quant_state[
param_name +
".quant_state.bitsandbytes__nf4"].cpu().data
return QuantState.from_dict(quant_state, device="cuda")

# Second iterate over all prequant and normal weights
Expand All @@ -842,8 +835,12 @@ def _parse_quant_state(param_name: str,
# Filter out all weights whose suffix is not ".weight"
if not weight_name.endswith(".weight"):
continue
if weight_name + ".quant_state.bitsandbytes__nf4" \
in temp_state_dict:

if (f"{weight_name}.quant_state.bitsandbytes__nf4" \
in temp_state_dict) or \
(f"{weight_name}.quant_state.bitsandbytes__fp4" \
in temp_state_dict):

quant_state = _parse_quant_state(weight_name,
temp_state_dict)
weight_name = weight_name.replace(".weight", ".qweight")
Expand Down