| """Separate normalized embedded MTP by byte-preserving safetensors repack. |
| |
| Avoids mlx-lm's presence-keyed RMSNorm shift on a converted trunk. No inference, |
| quantization, normalization, provider selection or source mutation is performed. |
| """ |
| from pathlib import Path |
| import argparse,hashlib,json,os,shutil,struct |
|
|
|
|
| def header(path): |
| with path.open('rb') as f: |
| length=struct.unpack('<Q',f.read(8))[0] |
| if length>16*1024**2:raise ValueError('Header size limit') |
| data=json.loads(f.read(length)) |
| return data,8+length |
|
|
|
|
| def repack(output,entries,heads): |
| metadata={'__metadata__':{'format':'mlx'}};cursor=0 |
| for newname,src,old,base,key in entries: |
| start,end=old['data_offsets'];metadata[newname]={**old,'data_offsets':[cursor,cursor+end-start]};cursor+=end-start |
| raw=json.dumps(metadata,separators=(',',':')).encode();raw+=b' '*(-len(raw)%8);digests={} |
| with output.open('xb') as out: |
| out.write(struct.pack('<Q',len(raw)));out.write(raw) |
| for newname,src,old,base,key in entries: |
| start,end=old['data_offsets'];count=end-start;digest=hashlib.sha256() |
| with src.open('rb') as source: |
| source.seek(base+start) |
| while count: |
| chunk=source.read(min(count,8*1024**2)) |
| if not chunk:raise ValueError('Truncated tensor') |
| out.write(chunk);digest.update(chunk);count-=len(chunk) |
| digests[newname]={'source_tensor':key,'payload_sha256':digest.hexdigest(),'payload_bytes':end-start} |
| return digests,cursor |
|
|
|
|
| def prepare(source,output): |
| source,output=Path(source).resolve(),Path(output).resolve() |
| if output.exists() or source==output or source in output.parents:raise ValueError('Output exists or inside source') |
| index=json.loads((source/'model.safetensors.index.json').read_text())['weight_map'];heads=[k for k in index if k.startswith('language_model.mtp.') or k.startswith('mtp.')] |
| if not heads:raise ValueError('No embedded MTP tensors') |
| schemas={} |
| for filename in sorted(set(index.values())): |
| if Path(filename).name!=filename:raise ValueError('Unsafe source shard') |
| h,base=header(source/filename);keys={k for k in h if k!='__metadata__'} |
| if keys!={k for k,v in index.items() if v==filename}:raise ValueError('Index/header mismatch') |
| if h.get('__metadata__',{}).get('format')!='mlx':raise ValueError('Source not marked normalized MLX format') |
| schemas[filename]=(h,base) |
| output.mkdir();mapping={};allhead=[];payloads={};total=0 |
| for filename,(h,base) in schemas.items(): |
| selected=[k for k,v in index.items() if v==filename];trunk=[k for k in selected if k not in heads] |
| for key in selected: |
| if key in heads: |
| newname=key.removeprefix('language_model.') |
| allhead.append((newname,source/filename,h[key],base,key)) |
| if not trunk:continue |
| if len(trunk)==len(selected): |
| os.link(source/filename,output/filename) |
| total+=sum(h[k]['data_offsets'][1]-h[k]['data_offsets'][0] for k in trunk) |
| else: |
| entries=[(k,source/filename,h[k],base,k) for k in trunk] |
| d,size=repack(output/filename,entries,heads);payloads.update(d);total+=size |
| mapping.update({k:filename for k in trunk}) |
| d,size=repack(output/'mtp.safetensors',allhead,heads);payloads.update(d) |
| for p in source.iterdir(): |
| if p.is_file() and p.suffix in ['.json','.jinja','.txt','.md'] and p.name not in ['model.safetensors.index.json']: |
| shutil.copy2(p,output/p.name) |
| (output/'model.safetensors.index.json').write_text(json.dumps({'metadata':{'total_size':total},'weight_map':mapping},indent=2)+'\n') |
| |
| for filename in [*{index[k] for k in heads if index[k] in mapping.values()},'mtp.safetensors']: |
| p=output/filename |
| if not p.exists():continue |
| h,base=header(p) |
| with p.open('rb') as f: |
| for name,record in h.items(): |
| if name=='__metadata__':continue |
| start,end=record['data_offsets'];f.seek(base+start);remaining=end-start;digest=hashlib.sha256() |
| while remaining: |
| block=f.read(min(remaining,8*1024**2));digest.update(block);remaining-=len(block) |
| if digest.hexdigest()!=payloads[name]['payload_sha256']:raise ValueError('Repacked tensor hash mismatch') |
| receipt={'method':'exact tensor-payload repack only; no numerical change', |
| 'source':str(source),'base_tensors':len(mapping),'mtp_tensors':len(heads),'payload_hashes':payloads, |
| 'norm_shift_applied':False,'quantization_changed':False,'source_unchanged':True} |
| (output/'mtp-separation-manifest.json').write_text(json.dumps(receipt,indent=2)+'\n');return receipt |
|
|
| if __name__=='__main__': |
| p=argparse.ArgumentParser();p.add_argument('--source',type=Path,required=True);p.add_argument('--output',type=Path,required=True);a=p.parse_args();r=prepare(a.source,a.output);print({k:r[k] for k in ['base_tensors','mtp_tensors','norm_shift_applied','quantization_changed']}) |
|
|
