#!/usr/bin/env python # This script extracts fp32 consolidated weights from a zero 2 and 3 DeepSpeed checkpoints. It gets # copied into the top level checkpoint dir, so the user can easily do the conversion at any point in # the future. Once extracted, the weights don't require DeepSpeed and can be used in any # application. # # example: python zero_to_fp32.py . pytorch_model.bin import argparse import torch import glob import math import os from collections import OrderedDict # while this script doesn't use deepspeed to recover data, since the checkpoints are pickled with # DeepSpeed data structures it has to be available in the current python environment. import deepspeed from deepspeed.utils import logger debug = 0 # load to cpu device = torch.device('cpu') def get_model_state_file(checkpoint_dir, zero_stage): if not os.path.isdir(checkpoint_dir): raise FileNotFoundError(f"Directory '{checkpoint_dir}' doesn't exist") # there should be only one file if zero_stage == 2: file = os.path.join(checkpoint_dir, "mp_rank_00_model_states.pt") elif zero_stage == 3: file = os.path.join(checkpoint_dir, "zero_pp_rank_0_mp_rank_00_model_states.pt") if not os.path.exists(file): raise FileNotFoundError(f"can't find model states file at '{file}'") return file def get_optim_files(checkpoint_dir): # XXX: need to test that this simple glob rule works for multi-node setup too optim_files = sorted(glob.glob(os.path.join(checkpoint_dir, "*_optim_states.pt"))) if len(optim_files) == 0: raise FileNotFoundError( f"can't find '*_optim_states.pt' files in directory '{checkpoint_dir}'") return optim_files def parse_model_state(file): state_dict = torch.load(file, map_location=device) if "buffer_names" not in state_dict: raise ValueError(f"{file} is not a model state checkpoint") buffer_names = state_dict["buffer_names"] if debug: print("Found buffers:", buffer_names) # recover just the buffers while restoring them to fp32 if they were saved in fp16 buffers = { k: v.float() for k, v in state_dict["module"].items() if k in buffer_names } return buffers def parse_optim_states(files, ds_checkpoint_dir): total_files = len(files) state_dicts = [] for f in files: state_dicts.append(torch.load(f, map_location=device)) if not "zero_stage" in state_dicts[0]['optimizer_state_dict']: raise ValueError(f"{files[0]} is not a zero checkpoint") zero_stage = state_dicts[0]['optimizer_state_dict']["zero_stage"] world_size = state_dicts[0]['optimizer_state_dict']["partition_count"] param_shapes = state_dicts[0]["param_shapes"] # For ZeRO-2 each param group can have different partition_count as data parallelism for expert # parameters can be different from data parallelism for non-expert parameters. So we can just # use the max of the partition_count to get the dp world_size. if type(world_size) is list: world_size = max(world_size) if world_size != total_files: raise ValueError( f"Expected {world_size} of '*_optim_states.pt' under '{ds_checkpoint_dir}' but found {total_files} files. " "Possibly due to an overwrite of an old checkpoint, or a checkpoint didn't get saved by one or more processes." ) # the groups are named differently in each stage if zero_stage == 2: fp32_groups_key = "single_partition_of_fp32_groups" elif zero_stage == 3: fp32_groups_key = "fp32_flat_groups" else: raise ValueError(f"unknown zero stage {zero_stage}") if zero_stage == 2: fp32_flat_groups = [ state_dicts[i]['optimizer_state_dict'][fp32_groups_key] for i in range(len(state_dicts)) ] elif zero_stage == 3: # if there is more than one param group, there will be multiple flattened tensors - one # flattened tensor per group - for simplicity merge them into a single tensor # # XXX: could make the script more memory efficient for when there are multiple groups - it # will require matching the sub-lists of param_shapes for each param group flattened tensor fp32_flat_groups = [ torch.cat(state_dicts[i]['optimizer_state_dict'][fp32_groups_key], 0) for i in range(len(state_dicts)) ] return zero_stage, world_size, param_shapes, fp32_flat_groups def _get_fp32_state_dict_from_zero_checkpoint(ds_checkpoint_dir): """ Returns fp32 state_dict reconstructed from ds checkpoint Args: - ``ds_checkpoint_dir``: path to the deepspeed checkpoint folder (where the optimizer files are) """ print(f"Processing zero checkpoint '{ds_checkpoint_dir}'") optim_files = get_optim_files(ds_checkpoint_dir) zero_stage, world_size, param_shapes, fp32_flat_groups = parse_optim_states(optim_files, ds_checkpoint_dir) print( f"Detected checkpoint of type zero stage {zero_stage}, world_size: {world_size}") model_file = get_model_state_file(ds_checkpoint_dir, zero_stage) buffers = parse_model_state(model_file) if zero_stage == 2: return _get_fp32_state_dict_from_zero2_checkpoint(world_size, param_shapes, fp32_flat_groups, buffers) elif zero_stage == 3: return _get_fp32_state_dict_from_zero3_checkpoint(world_size, param_shapes, fp32_flat_groups, buffers) def _get_fp32_state_dict_from_zero2_checkpoint(world_size, param_shapes, fp32_flat_groups, buffers): # Reconstruction protocol: # # XXX: document this if debug: for i in range(world_size): for j in range(len(fp32_flat_groups[0])): print(f"fp32_flat_groups[{i}][{j}].shape={fp32_flat_groups[i][j].shape}") # XXX: memory usage doubles here (zero2) num_param_groups = len(fp32_flat_groups[0]) merged_single_partition_of_fp32_groups = [] for i in range(num_param_groups): merged_partitions = [sd[i] for sd in fp32_flat_groups] full_single_fp32_vector = torch.cat(merged_partitions, 0) merged_single_partition_of_fp32_groups.append(full_single_fp32_vector) avail_numel = sum([ full_single_fp32_vector.numel() for full_single_fp32_vector in merged_single_partition_of_fp32_groups ]) if debug: wanted_params = sum([len(shapes) for shapes in param_shapes]) wanted_numel = sum( [sum(shape.numel() for shape in shapes.values()) for shapes in param_shapes]) # not asserting if there is a mismatch due to possible padding print(f"Have {avail_numel} numels to process.") print(f"Need {wanted_numel} numels in {wanted_params} params.") state_dict = OrderedDict() # buffers state_dict.update(buffers) if debug: print(f"added {len(buffers)} buffers") # params # XXX: for huge models that can't fit into the host's RAM we will have to recode this to support # out-of-core computing solution total_numel = 0 total_params = 0 for shapes, full_single_fp32_vector in zip(param_shapes, merged_single_partition_of_fp32_groups): offset = 0 avail_numel = full_single_fp32_vector.numel() for name, shape in shapes.items(): unpartitioned_numel = shape.numel() total_numel += unpartitioned_numel total_params += 1 if debug: print( f"{name} full shape: {shape} unpartitioned numel {unpartitioned_numel} " ) state_dict[name] = full_single_fp32_vector.narrow( 0, offset, unpartitioned_numel).view(shape) offset += unpartitioned_numel # Z2 started to align to 2*world_size to improve nccl performance. Therefore both offset and # avail_numel can differ by anywhere between 0..2*world_size. Due to two unrelated complex # paddings performed in the code it's almost impossible to predict the exact numbers w/o the # live optimizer object, so we are checking that the numbers are within the right range align_to = 2 * world_size def zero2_align(x): return align_to * math.ceil(x / align_to) if debug: print(f"original offset={offset}, avail_numel={avail_numel}") offset = zero2_align(offset) avail_numel = zero2_align(avail_numel) if debug: print(f"aligned offset={offset}, avail_numel={avail_numel}") # Sanity check if offset != avail_numel: raise ValueError( f"consumed {offset} numels out of {avail_numel} - something is wrong") print( f"Reconstructed fp32 state dict with {total_params} params {total_numel} elements" ) return state_dict def zero3_partitioned_param_info(unpartitioned_numel, world_size): remainder = unpartitioned_numel % world_size padding_numel = (world_size - remainder) if remainder else 0 partitioned_numel = math.ceil(unpartitioned_numel / world_size) return partitioned_numel, padding_numel def _get_fp32_state_dict_from_zero3_checkpoint(world_size, param_shapes, fp32_flat_groups, buffers): # Reconstruction protocol: For zero3 we need to zip the partitions together at boundary of each # param, re-consolidating each param, while dealing with padding if any avail_numel = fp32_flat_groups[0].numel() * world_size # merge list of dicts, preserving order param_shapes = {k: v for d in param_shapes for k, v in d.items()} if debug: for i in range(world_size): print(f"fp32_flat_groups[{i}].shape={fp32_flat_groups[i].shape}") wanted_params = len(param_shapes) wanted_numel = sum(shape.numel() for shape in param_shapes.values()) # not asserting if there is a mismatch due to possible padding print(f"Have {avail_numel} numels to process.") print(f"Need {wanted_numel} numels in {wanted_params} params.") state_dict = OrderedDict() # buffers state_dict.update(buffers) if debug: print(f"added {len(buffers)} buffers") # params # XXX: for huge models that can't fit into the host's RAM we will have to recode this to support # out-of-core computing solution offset = 0 total_numel = 0 total_params = 0 for name, shape in param_shapes.items(): unpartitioned_numel = shape.numel() total_numel += unpartitioned_numel total_params += 1 partitioned_numel, partitioned_padding_numel = zero3_partitioned_param_info(unpartitioned_numel, world_size) if debug: print( f"{total_params} {name} full shape: {shape} partition0 numel={partitioned_numel} partitioned_padding_numel={partitioned_padding_numel}" ) # XXX: memory usage doubles here state_dict[name] = torch.cat( tuple(fp32_flat_groups[i].narrow(0, offset, partitioned_numel) for i in range(world_size)), 0).narrow(0, 0, unpartitioned_numel).view(shape) offset += partitioned_numel offset *= world_size # Sanity check if offset != avail_numel: raise ValueError( f"consumed {offset} numels out of {avail_numel} - something is wrong") print( f"Reconstructed fp32 state dict with {total_params} params {total_numel} elements" ) return state_dict def get_fp32_state_dict_from_zero_checkpoint(checkpoint_dir, tag=None): """ Convert ZeRO 2 or 3 checkpoint into a single fp32 consolidated state_dict that can be loaded with ``load_state_dict()`` and used for training without DeepSpeed or shared with others, for example via a model hub. Args: - ``checkpoint_dir``: path to the desired checkpoint folder - ``tag``: checkpoint tag used as a unique identifier for checkpoint. If not provided will attempt to load tag in 'latest' file. e.g., ``global_step14`` Returns: - pytorch ``state_dict`` Note: this approach may not work if your application doesn't have sufficient free CPU memory and you may need to use the offline approach using the ``zero_to_fp32.py`` script that is saved with the checkpoint. A typical usage might be :: from deepspeed.utils.zero_to_fp32 import get_fp32_state_dict_from_zero_checkpoint # do the training and checkpoint saving state_dict = get_fp32_state_dict_from_zero_checkpoint(checkpoint_dir) # already on cpu model = model.cpu() # move to cpu model.load_state_dict(state_dict) # submit to model hub or save the model to share with others In this example the ``model`` will no longer be usable in the deepspeed context of the same application. i.e. you will need to re-initialize the deepspeed engine, since ``model.load_state_dict(state_dict)`` will remove all the deepspeed magic from it. If you want it all done for you, use ``load_state_dict_from_zero_checkpoint`` instead. """ if tag is None: latest_path = os.path.join(checkpoint_dir, 'latest') if os.path.isfile(latest_path): with open(latest_path, 'r') as fd: tag = fd.read().strip() else: raise ValueError(f"Unable to find 'latest' file at {latest_path}") ds_checkpoint_dir = os.path.join(checkpoint_dir, tag) if not os.path.isdir(ds_checkpoint_dir): raise FileNotFoundError(f"Directory '{ds_checkpoint_dir}' doesn't exist") return _get_fp32_state_dict_from_zero_checkpoint(ds_checkpoint_dir) def convert_zero_checkpoint_to_fp32_state_dict(checkpoint_dir, output_file, tag=None): """ Convert ZeRO 2 or 3 checkpoint into a single fp32 consolidated ``state_dict`` file that can be loaded with ``torch.load(file)`` + ``load_state_dict()`` and used for training without DeepSpeed. Args: - ``checkpoint_dir``: path to the desired checkpoint folder. (one that contains the tag-folder, like ``global_step14``) - ``output_file``: path to the pytorch fp32 state_dict output file (e.g. path/pytorch_model.bin) - ``tag``: checkpoint tag used as a unique identifier for checkpoint. If not provided will attempt to load tag in the file named ``latest`` in the checkpoint folder, e.g., ``global_step14`` """ state_dict = get_fp32_state_dict_from_zero_checkpoint(checkpoint_dir, tag) print(f"Saving fp32 state dict to {output_file}") torch.save(state_dict, output_file) def load_state_dict_from_zero_checkpoint(model, checkpoint_dir, tag=None): """ 1. Put the provided model to cpu 2. Convert ZeRO 2 or 3 checkpoint into a single fp32 consolidated ``state_dict`` 3. Load it into the provided model Args: - ``model``: the model object to update - ``checkpoint_dir``: path to the desired checkpoint folder. (one that contains the tag-folder, like ``global_step14``) - ``tag``: checkpoint tag used as a unique identifier for checkpoint. If not provided will attempt to load tag in the file named ``latest`` in the checkpoint folder, e.g., ``global_step14`` Returns: - ``model`: modified model Make sure you have plenty of CPU memory available before you call this function. If you don't have enough use the ``zero_to_fp32.py`` utility to do the conversion. You will find it conveniently placed for you in the checkpoint folder. A typical usage might be :: from deepspeed.utils.zero_to_fp32 import load_state_dict_from_zero_checkpoint model = load_state_dict_from_zero_checkpoint(trainer.model, checkpoint_dir) # submit to model hub or save the model to share with others Note, that once this was run, the ``model`` will no longer be usable in the deepspeed context of the same application. i.e. you will need to re-initialize the deepspeed engine, since ``model.load_state_dict(state_dict)`` will remove all the deepspeed magic from it. """ logger.info(f"Extracting fp32 weights") state_dict = get_fp32_state_dict_from_zero_checkpoint(checkpoint_dir, tag) logger.info(f"Overwriting model with fp32 weights") model = model.cpu() model.load_state_dict(state_dict, strict=False) return model if __name__ == "__main__": parser = argparse.ArgumentParser() parser.add_argument( "checkpoint_dir", type=str, help="path to the desired checkpoint folder, e.g., path/checkpoint-12") parser.add_argument( "output_file", type=str, help= "path to the pytorch fp32 state_dict output file (e.g. path/checkpoint-12/pytorch_model.bin)" ) parser.add_argument("-d", "--debug", action='store_true', help="enable debug") args = parser.parse_args() debug = args.debug convert_zero_checkpoint_to_fp32_state_dict(args.checkpoint_dir, args.output_file)