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2026-01-09 13:34:11 +08:00
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import argparse
import glob
import json
import os
from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple
import numpy as np
import torch
from safetensors.torch import safe_open
from vllm.model_executor.layers.quantization.schema import QuantParamSchema
# Adapted from vllm/model_executor/model_loader/weight_utils.py
# The main differences are that we add the NPZ format and simplify
# its functionality drastically for our purposes (e.g. we assume that
# the quantized model exists locally and there is no need to download it)
def _prepare_hf_weights(
quantized_model_dir: str,
load_format: str = "auto",
fall_back_to_pt: bool = True,
) -> Tuple[str, List[str], bool]:
if not os.path.isdir(quantized_model_dir):
raise FileNotFoundError(
f"The quantized model directory `{quantized_model_dir}` "
"does not exist.")
use_safetensors = False
# Some quantized models use .pt files for storing the weights.
if load_format == "auto":
allow_patterns = ["*.safetensors", "*.bin"]
elif load_format == "safetensors":
use_safetensors = True
allow_patterns = ["*.safetensors"]
elif load_format == "pt":
allow_patterns = ["*.pt"]
elif load_format == "npz":
allow_patterns = ["*.npz"]
else:
raise ValueError(f"Unknown load_format: {load_format}")
if fall_back_to_pt:
allow_patterns += ["*.pt"]
hf_weights_files: List[str] = []
for pattern in allow_patterns:
hf_weights_files += glob.glob(
os.path.join(quantized_model_dir, pattern))
if len(hf_weights_files) > 0:
if pattern == "*.safetensors":
use_safetensors = True
break
if not use_safetensors:
# Exclude files that are not needed for inference.
# https://github.com/huggingface/transformers/blob/v4.34.0/src/transformers/trainer.py#L227-L233
blacklist = [
"training_args.bin",
"optimizer.bin",
"optimizer.pt",
"scheduler.pt",
"scaler.pt",
]
hf_weights_files = [
f for f in hf_weights_files
if not any(f.endswith(x) for x in blacklist)
]
if len(hf_weights_files) == 0:
raise RuntimeError(
f"Cannot find any model weights with `{quantized_model_dir}`")
return hf_weights_files, use_safetensors
# Adapted from vllm/model_executor/model_loader/weight_utils.py
def _hf_tensorfile_iterator(filename: str, load_format: str,
use_safetensors: bool):
if load_format == "npz":
assert not use_safetensors
with np.load(filename) as data:
for name in data.files:
param = torch.from_numpy(data[name])
yield name, param
elif use_safetensors:
with safe_open(filename, framework="pt") as f:
for name in f.keys(): # NOQA: SIM118
param = f.get_tensor(name)
yield name, param
else:
state = torch.load(filename, map_location="cpu")
for name, param in state.items():
yield name, param
del state
torch.cuda.empty_cache()
def _kv_scales_extractor(
hf_tensor_files: Iterable[str],
use_safetensors: bool,
rank_keyword: str = "rank",
expected_tp_size: Optional[int] = None) -> Dict[int, Dict[int, float]]:
"""
Given a list of files containing tensor data, attempt to extract KV cache
scales from these files. Intended as a helper function taking in the output
from _prepare_hf_weights.
Args:
rank_keyword Matches the number immediately after this keyword in the
tensor filename to determine the TP rank corresponding
to said tensor file
expected_tp_size If specified, the TP size of the tensor files is checked
against this and an error is raised if they don't match.
Returns a dictionary mapping TP ranks to their relevant KV cache scales.
The per-rank scales are themselves represented as a dictionary of layer
indices to the respective per-layer scale.
"""
for char in rank_keyword:
assert not char.isdecimal(
), f"Rank keyword {rank_keyword} contains a numeric character!"
rank_scales_map = {}
for tensor_file in hf_tensor_files:
try:
rank_idx = tensor_file.find(rank_keyword)
if rank_idx != -1:
start_idx = rank_idx + len(rank_keyword)
stop_idx = start_idx
while stop_idx < len(
tensor_file) and tensor_file[stop_idx].isdecimal():
stop_idx += 1
if stop_idx == start_idx:
raise RuntimeError("Did not find rank # in filename.")
rank = int(tensor_file[start_idx:stop_idx])
elif len(hf_tensor_files) == 1:
# Since there is only one tensor file, we can assume
# that it's intended for TP rank 0
rank = 0
else:
raise RuntimeError(
f"Filename does not contain '{rank_keyword}'.")
except RuntimeError:
print("Unable to determine TP rank "
f"corresponding to file '{tensor_file}'")
raise
if rank not in rank_scales_map:
layer_scales_map = {}
rank_scales_map[rank] = layer_scales_map
else:
raise RuntimeError(
f"Tensor file '{tensor_file}' shares TP rank {rank} "
"with another tensor file.")
module_delimiter = ":" if args.load_format == "npz" else "."
for name, param in _hf_tensorfile_iterator(tensor_file,
args.load_format,
use_safetensors):
if "kv_cache_scaling_factor" in name:
nums = [
int(s) for s in name.split(module_delimiter)
if s.isdecimal()
]
assert len(
nums) == 1, f"Could not determine layer idx for {name}"
layer_idx = nums[0]
assert layer_idx not in layer_scales_map, f"Duplicate scaling"\
f" factor corresponding to layer {layer_idx}"
try:
layer_scales_map[layer_idx] = param.item()
except RuntimeError:
print(
"This utility supports only per-tensor scalar scales "
f"for now. The tensor\n {name} = {param} \nis an "
"invalid scale factor.")
raise
if all(
len(layer_scales_map) == 0
for layer_scales_map in rank_scales_map.values()):
# Note: this is true even if the rank_scales_map is empty
print("WARNING: No KV cache scale factors found. No output saved.")
return None
empirical_tp_world_size = max(rank_scales_map.keys()) + 1
if expected_tp_size is not None:
assert expected_tp_size == empirical_tp_world_size, \
f"User expected TP world size = {expected_tp_size} " \
"from model but tool is expecting TP world size = " \
f"{empirical_tp_world_size} from model instead."
for i in range(empirical_tp_world_size):
assert i in rank_scales_map, "Expected TP world size = "\
f"{empirical_tp_world_size} but did not find KV " \
f"cache scaling factors for TP rank {i}"
print(f"Found TP world size = {empirical_tp_world_size} "
"when extracting KV cache scales!")
return rank_scales_map
def _metadata_extractor(quantized_model_dir: str,
metadata_extract_fns: \
Dict[str, Callable[[Dict[str, Any]], Any]]) \
-> Dict[str, Any]:
"""
Given a directory containing quantized model files, this function
aims to extract metadata from the JSON files within this directory.
Each JSON file is expected to represent a dictionary in JSON
format (referred to as a "JSON-dictionary"). Metadata extraction is
defined by a dictionary called metadata_extract_fns, where each
metadata field name is mapped to an extraction function.
These extraction functions are designed to take a JSON-dictionary
as their only argument and return the corresponding metadata.
While extraction functions are permitted to raise exceptions, they
should only raise a KeyError or ValueError if the metadata field
cannot be extracted from the current JSON-dictionary, yet there's
a possibility of finding it in another JSON-dictionary.
The function returns a dictionary that maps metadata fields to
their extracted data. The keys of this dictionary correspond exactly
to those in metadata_extract_fns. If any fields fail to be extracted,
their corresponding values are set to None, and a warning is printed.
"""
if not os.path.isdir(quantized_model_dir):
raise FileNotFoundError(
f"The quantized model directory `{quantized_model_dir}` "
"does not exist.")
metadata_files = glob.glob(os.path.join(quantized_model_dir, "*.json"))
result = {}
for file in metadata_files:
with open(file) as f:
try:
metadata = json.load(f)
except json.JSONDecodeError:
print(f"Could not parse `{file}` as a valid metadata file,"
" skipping it.")
continue
if not isinstance(metadata, dict):
print(f"The file `{file}` does not correspond to a "
"JSON-serialized dictionary, skipping it.")
continue
for metadata_name, extract_fn in metadata_extract_fns.items():
try:
metadata_info = extract_fn(metadata)
if metadata_name not in result:
result[metadata_name] = metadata_info
elif metadata_info != result[metadata_name]:
raise RuntimeError(
"Metadata mismatch! Originally found "
f"{metadata_name} = {result[metadata_name]} but "
f"now found {metadata_name} = {metadata_info} in "
f"`{file}`")
except KeyError:
# It is possible that a given file does not contain some
# of our selected metadata as it could be located in some
# other metadata file.
# 'EFINAE': extract_fn failure is not an error.
pass
except ValueError:
# See above.
pass
# Warn if we cannot find any of the requested metadata
for metadata_name in metadata_extract_fns:
if metadata_name not in result:
print("WARNING: Unable to find requested metadata field "
f"`{metadata_name}`, setting it to None.")
result[metadata_name] = None
return result
def main(args):
metadata_extract_fns = {
"model_type": lambda json_dict: json_dict["layers"][0]["decoder_type"],
"tp_size": lambda json_dict: int(json_dict["tensor_parallel"]),
"model_dtype": lambda json_dict: json_dict["dtype"]
}
recovered_metadata = _metadata_extractor(args.quantized_model,
metadata_extract_fns)
if args.tp_size is not None:
metadata_tp_size = recovered_metadata["tp_size"]
if metadata_tp_size is not None:
assert args.tp_size == metadata_tp_size, \
f"User expected TP world size = {args.tp_size} " \
f"but found TP world size = {metadata_tp_size} from metadata!"
expected_tp_size = args.tp_size or recovered_metadata["tp_size"]
rank_keyword = "rank"
hf_tensor_files, use_safetensors = _prepare_hf_weights(
args.quantized_model, args.load_format)
rank_scales_map = _kv_scales_extractor(hf_tensor_files, use_safetensors,
rank_keyword, expected_tp_size)
# Postprocess: formatting to the current schema. Consider pulling it
# out into a dedicated function should it ever become more complicated.
rank_scales_map = {
rank: {k: scale[k]
for k in sorted(scale.keys())}
for rank, scale in rank_scales_map.items()
}
# TODO: Expand this with activation and weights scaling factors when
# they are used in the future
schema = QuantParamSchema(
model_type=recovered_metadata["model_type"],
kv_cache={
"dtype": ("float8_e4m3fn" if len(rank_scales_map) > 0 else
recovered_metadata["model_dtype"]),
"scaling_factor":
rank_scales_map
},
)
if args.output_dir is None:
output_file = os.path.join(args.quantized_model, args.output_name)
else:
if not os.path.isdir(args.output_dir):
os.makedirs(args.output_dir, exist_ok=True)
output_file = os.path.join(args.output_dir, args.output_name)
with open(output_file, 'w') as f:
f.write(schema.model_dump_json(indent=4))
print(f"Completed! KV cache scaling factors saved to {output_file}")
if __name__ == "__main__":
parser = argparse.ArgumentParser(
description="This simple utility extracts the "
"KV cache scaling factors from a quantized HF model "
"and saves them to a JSON file compatible with later "
"use by vLLM (pass this file to the appropriate "
"runtime typically using the argument "
"--quantization-param-path <filename>). This is only used "
"if the KV cache dtype is FP8 and on ROCm (AMD GPU).")
parser.add_argument(
"--quantized_model",
help="Specify the directory containing a single quantized HF model. "
"It is expected that the quantization format is FP8_E4M3, for use "
"on ROCm (AMD GPU).",
required=True)
parser.add_argument(
"--load_format",
help="Optionally specify the format of the model's tensor files "
"containing the KV cache scaling factors.",
choices=["auto", "safetensors", "npz", "pt"],
default="auto")
parser.add_argument(
"--output_dir",
help="Optionally specify the output directory. By default the "
"KV cache scaling factors will be saved in the model directory, "
"however you can override this behavior here.",
default=None)
parser.add_argument(
"--output_name",
help="Optionally specify the output filename.",
# TODO: Change this once additional scaling factors are enabled
default="kv_cache_scales.json")
parser.add_argument(
"--tp_size",
help="Optionally specify the tensor-parallel (TP) size that the "
"quantized model should correspond to. If specified, during KV "
"cache scaling factor extraction the observed TP size will be "
"checked against this and an error will be raised if there is "
"a mismatch. If not specified, the quantized model's expected "
"TP size is instead inferred from the largest TP rank observed. "
"The expected TP size is cross-checked against the TP ranks "
"observed in the quantized model and an error is raised if any "
"discrepancies are found.",
default=None,
type=int)
args = parser.parse_args()
main(args)