246 lines
8.5 KiB
Python
246 lines
8.5 KiB
Python
# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
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# SPDX-License-Identifier: Apache-2.0
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"""
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Usage:
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------
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python convert_k2_thinking_int4_to_bf16.py [-h] --model-dir MODEL_DIR [--output-dir OUTPUT_DIR]
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[--files FILE [FILE ...]] [--config-path CONFIG_PATH]
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[--overwrite]
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options:
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-h, --help Show this help message and exit.
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--model-dir MODEL_DIR Path to the directory of the HF safetensors quantized model.
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--output-dir OUTPUT_DIR
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Path to the directory to save the converted BF16 model.
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Default: <model-dir>_bf16
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--files FILE [FILE ...]
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Specific safetensors filenames to convert (relative to model-dir).
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Convert all if omitted.
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--config-path CONFIG_PATH
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Path to config.json to extract group_size (default: model-dir/config.json).
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--overwrite Rewrite output files even if they already exist.
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Example:
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--------
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python convert_k2_thinking_int4_to_bf16.py --model-dir /Kimi-K2-Thinking --output-dir /Kimi-K2-Thinking-bf16
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"""
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import argparse
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import json
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import os
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import shutil
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from collections import defaultdict
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import torch
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from compressed_tensors.compressors import unpack_from_int32
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from safetensors.torch import safe_open, save_file
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from tqdm import tqdm
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def _load_config(model_dir: str, config_path: str | None) -> tuple[int, int, int]:
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"""Read config.json and return hidden_size, inter_size, and group_size."""
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cfg_path = config_path or os.path.join(model_dir, "config.json")
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with open(cfg_path) as f:
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cfg = json.load(f)
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hidden_size = int(cfg.get("hidden_size"))
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inter_size = int(cfg.get("moe_intermediate_size"))
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group_size = int(
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cfg.get("quantization_config", {})
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.get("config_groups", {})
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.get("group_0", {})
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.get("weights", {})
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.get("group_size", 128)
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)
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return hidden_size, inter_size, group_size
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def _dequantize_tensor(
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weight_packed: torch.Tensor,
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weight_scale: torch.Tensor,
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weight_shape: torch.Tensor,
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group_size: int,
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) -> torch.Tensor:
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"""Unpack int32 quantized tensor and multiply with scales to create BF16 tensor."""
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if isinstance(weight_shape, torch.Tensor):
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shape = tuple(int(v) for v in weight_shape.view(-1).tolist())
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else:
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shape = tuple(weight_shape)
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weight = unpack_from_int32(weight_packed, 4, shape)
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if group_size > 0:
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scale = weight_scale.to(torch.float32)
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if scale.dim() == 1:
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scale = scale.unsqueeze(1)
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scales = torch.repeat_interleave(scale, repeats=group_size, dim=1)
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else:
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scales = weight_scale.to(torch.float32)
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if scales.shape != weight.shape:
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if scales.numel() == weight.numel():
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scales = scales.reshape_as(weight)
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else:
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raise ValueError(f"Scale shape {scales.shape} incompatible with weight shape {weight.shape}")
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bf16 = (weight.to(torch.float32) * scales).to(torch.bfloat16)
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return bf16.contiguous()
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def _is_quantized_weight_key(key: str) -> bool:
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"""Check if the key is a quantized MoE expert weight key."""
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if ".mlp.experts." not in key or ".shared_experts." in key:
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return False
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suffixes = ("weight_packed", "weight_scale", "weight_shape")
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for proj in ("gate_proj", "up_proj", "down_proj"):
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for suffix in suffixes:
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if key.endswith(f".{proj}.{suffix}"):
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return True
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return False
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def convert_file(
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input_path: str,
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output_path: str,
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group_size: int,
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skip_existing: bool = True,
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):
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"""Convert a single safetensors file from quantized format to BF16 (GPU accelerated)."""
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if skip_existing and os.path.exists(output_path):
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return
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tensors = {}
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expert_buffers = defaultdict(lambda: defaultdict(dict))
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# Load weights directly on GPU
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with safe_open(input_path, framework="pt", device="cuda") as reader:
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keys = list(reader.keys())
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for key in keys:
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tensor = reader.get_tensor(key)
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if not _is_quantized_weight_key(key):
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tensors[key] = tensor
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continue
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parts = key.split(".")
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try:
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expert_idx = parts.index("experts")
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except ValueError:
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tensors[key] = tensor
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continue
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prefix = ".".join(parts[: expert_idx + 2])
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project = parts[-2]
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suffix = parts[-1]
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expert_buffers[prefix][project][suffix] = tensor
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# Convert quantized weights
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for prefix, components in expert_buffers.items():
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for proj_name in ["gate_proj", "up_proj", "down_proj"]:
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proj_data = components.get(proj_name, {})
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required = {"weight_packed", "weight_scale", "weight_shape"}
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if not required.issubset(proj_data.keys()):
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# Keep quantized tensors if incomplete
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for suffix, value in proj_data.items():
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tensors[f"{prefix}.{proj_name}.{suffix}"] = value
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continue
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# Dequantize to BF16
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bf16_weight = _dequantize_tensor(
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proj_data["weight_packed"].to(torch.int32),
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proj_data["weight_scale"].to(torch.float32),
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proj_data["weight_shape"],
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group_size,
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)
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tensors[f"{prefix}.{proj_name}.weight"] = bf16_weight.to(torch.bfloat16)
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# Save converted file (moved to CPU for compatibility)
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cpu_tensors = {k: v.cpu() for k, v in tensors.items()}
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os.makedirs(os.path.dirname(output_path), exist_ok=True)
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save_file(cpu_tensors, output_path)
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def parse_args() -> argparse.Namespace:
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parser = argparse.ArgumentParser(description="Convert GPTQ MoE experts to BF16 weights.")
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parser.add_argument("--model-dir", required=True, help="Directory containing safetensors checkpoints.")
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parser.add_argument(
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"--output-dir",
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default=None,
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help="Destination BF16 model directory (default: <model-dir>_bf16).",
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)
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parser.add_argument(
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"--files",
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nargs="+",
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default=None,
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help="Optional specific safetensor files to convert.",
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)
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parser.add_argument(
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"--config-path",
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default=None,
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help="Path to config.json if not in model-dir.",
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)
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parser.add_argument(
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"--overwrite",
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action="store_true",
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help="Overwrite existing BF16 files.",
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)
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return parser.parse_args()
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def main():
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args = parse_args()
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model_dir = os.path.abspath(args.model_dir)
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output_dir = os.path.abspath(args.output_dir or f"{model_dir}_bf16")
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if not os.path.isdir(model_dir):
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raise FileNotFoundError(f"Model directory not found: {model_dir}")
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_, _, group_size = _load_config(model_dir, args.config_path)
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# Collect target files
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if args.files:
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targets = [os.path.join(model_dir, fname) for fname in args.files]
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else:
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targets = [
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os.path.join(model_dir, name) for name in sorted(os.listdir(model_dir)) if name.endswith(".safetensors")
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]
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if not targets:
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print("No safetensors checkpoints found.")
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return
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# Convert with progress bar
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for path in tqdm(targets, desc="Converting weights", unit="file"):
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if not os.path.isfile(path):
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continue
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rel = os.path.relpath(path, model_dir)
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output_path = os.path.join(output_dir, rel)
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convert_file(path, output_path, group_size, skip_existing=not args.overwrite)
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# Copy config/json/py/tokenizer
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for fname in os.listdir(model_dir):
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src_path = os.path.join(model_dir, fname)
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dst_path = os.path.join(output_dir, fname)
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if fname == "model.safetensors.index.json":
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continue
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if fname.endswith(".json") or fname.endswith(".py") or fname.startswith("tokenizer"):
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shutil.copy2(src_path, dst_path)
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# Generate new index
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new_index_path = os.path.join(output_dir, "model.safetensors.index.json")
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weight_map = {}
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for fname in sorted(os.listdir(output_dir)):
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if not fname.endswith(".safetensors"):
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continue
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safetensor_path = os.path.join(output_dir, fname)
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with safe_open(safetensor_path, framework="pt") as reader:
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for key in reader.keys():
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weight_map[key] = fname
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with open(new_index_path, "w") as f:
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json.dump({"metadata": {}, "weight_map": weight_map}, f, indent=2)
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print(f"\nSuccessful! Output saved to: {output_dir}")
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if __name__ == "__main__":
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main()
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