Source code for deepspeed.runtime.pipe.module

import os
import glob
import enum

import re as regex

from collections import defaultdict
from functools import partial

import torch
import torch.nn as nn
import torch.distributed as dist

from deepspeed.utils import logger
from .. import utils as ds_utils
from ..activation_checkpointing import checkpointing
from .topology import PipeDataParallelTopology, PipelineParallelGrid
from deepspeed.runtime.state_dict_factory import SDLoaderFactory


class PipelineError(Exception):
    """Errors related to the use of deepspeed.PipelineModule """


[docs]class LayerSpec: """Building block for specifying pipeline-parallel modules. LayerSpec stores the type information and parameters for each stage in a PipelineModule. For example: .. code-block:: python nn.Sequence( torch.nn.Linear(self.in_dim, self.hidden_dim, bias=False), torch.nn.Linear(self.hidden_hidden, self.out_dim) ) becomes .. code-block:: python layer_specs = [ LayerSpec(torch.nn.Linear, self.in_dim, self.hidden_dim, bias=False), LayerSpec(torch.nn.Linear, self.hidden_hidden, self.out_dim)] ] """ def __init__(self, typename, *module_args, **module_kwargs): self.typename = typename self.module_args = module_args self.module_kwargs = module_kwargs if not issubclass(typename, nn.Module): raise RuntimeError('LayerSpec only supports torch.nn.Module types.') if dist.is_initialized(): self.global_rank = dist.get_rank() else: self.global_rank = -1 def __repr__(self): return ds_utils.call_to_str(self.typename.__name__, self.module_args, self.module_kwargs)
[docs] def build(self, log=False): """Build the stored specification.""" if log: logger.info(f'RANK={self.global_rank} building {repr(self)}') return self.typename(*self.module_args, **self.module_kwargs)
[docs]class TiedLayerSpec(LayerSpec): def __init__(self, key, typename, *module_args, forward_fn=None, tied_weight_attr='weight', **module_kwargs): super().__init__(typename, *module_args, **module_kwargs) self.key = key self.forward_fn = forward_fn self.tied_weight_attr = tied_weight_attr
[docs]class PipelineModule(nn.Module): def __init__(self, layers, num_stages=None, topology=None, loss_fn=None, seed_layers=False, seed_fn=None, base_seed=1234, partition_method='parameters', activation_checkpoint_interval=0, activation_checkpoint_func=checkpointing.checkpoint, checkpointable_layers=None): """Modules to be parallelized with pipeline parallelism. The key constraint that enables pipeline parallelism is the representation of the forward pass as a sequence of layers and the enforcement of a simple interface between them. The forward pass is implicitly defined by the module ``layers``. The key assumption is that the output of each layer can be directly fed as input to the next, like a ``torch.nn.Sequence``. The forward pass is implicitly: .. code-block:: python def forward(self, inputs): x = inputs for layer in self.layers: x = layer(x) return x .. note:: Pipeline parallelism is not compatible with ZeRO-2 and ZeRO-3. Args: layers (Iterable): A sequence of layers defining pipeline structure. Can be a ``torch.nn.Sequential`` module. num_stages (int, optional): The degree of pipeline parallelism. If not specified, ``topology`` must be provided. topology (``deepseed.runtime.pipe.ProcessTopology``, optional): Defines the axes of parallelism axes for training. Must be provided if ``num_stages`` is ``None``. loss_fn (callable, optional): Loss is computed ``loss = loss_fn(outputs, label)`` base_seed (int, optional): [description]. Defaults to 1234. partition_method (str, optional): [description]. Defaults to 'parameters'. activation_checkpoint_interval (int, optional): The granularity activation checkpointing in terms of number of layers. 0 disables activation checkpointing. activation_checkpoint_func (callable, optional): The function to use for activation checkpointing. Defaults to ``deepspeed.checkpointing.checkpoint``. """ super().__init__() if num_stages is None and topology is None: raise RuntimeError('must provide num_stages or topology') self.micro_offset = 0 self.loss_fn = loss_fn self.checkpointable_layers = checkpointable_layers if checkpointable_layers is not None: assert isinstance(checkpointable_layers, list), "param `checkpointable_layers` must be type of list." self.seed_layers = seed_layers self.seed_fn = seed_fn self.base_seed = base_seed if dist.get_rank() == 0: try: seed_str = self.seed_fn.__name__ except AttributeError: seed_str = None print( f'SEED_LAYERS={self.seed_layers} BASE_SEED={self.base_seed} SEED_FN={seed_str}' ) # Setup world info self.world_group = dist.new_group(ranks=range(dist.get_world_size())) self.global_rank = dist.get_rank(group=self.world_group) self.world_size = dist.get_world_size(group=self.world_group) self.local_rank = int(os.environ.get("LOCAL_RANK", None)) assert self.local_rank != None if topology: self._topo = topology self.num_stages = self._topo.get_dim('pipe') else: self.num_stages = num_stages if topology is None: if self.world_size % self.num_stages != 0: raise RuntimeError( f'num_stages ({self.num_stages}) must divide distributed world size ({self.world_size})' ) dp = self.world_size // num_stages topology = PipeDataParallelTopology(num_pp=num_stages, num_dp=dp) self._topo = topology # Construct communicators for pipeline topology self._grid = PipelineParallelGrid(process_group=self.world_group, topology=self._topo) self.stage_id = self._topo.get_coord(self.global_rank).pipe # Initialize partition information self._layer_specs = list(layers) self._num_layers = len(self._layer_specs) self._local_start = 0 self._local_stop = None self._partition_layers(method=partition_method) self.forward_funcs = [] self.tied_modules = nn.ModuleDict() self.tied_weight_attrs = {} # Offset the random seed by the stage ID. #newseed = torch.cuda.initial_seed() + self._grid.get_stage_id() #ds_utils.set_random_seed(newseed) #with torch.random.fork_rng(devices=[torch.cuda.current_device()]): self._build() self.to(f'cuda:{self.local_rank}') self.tied_comms = self._index_tied_modules() self._synchronize_tied_weights() self.activation_checkpoint_interval = activation_checkpoint_interval self.activation_checkpoint_func = activation_checkpoint_func def _build(self): specs = self._layer_specs for local_idx, layer in enumerate(specs[self._local_start:self._local_stop]): layer_idx = local_idx + self._local_start if self.seed_layers: if self.seed_fn: self.seed_fn(self.base_seed + layer_idx) else: ds_utils.set_random_seed(self.base_seed + layer_idx) # Recursively build PipelineModule objects if isinstance(layer, PipelineModule): raise NotImplementedError('RECURSIVE BUILD NOT YET IMPLEMENTED') # LayerSpec objects contain an nn.Module that should be allocated now. elif isinstance(layer, nn.Module): name = str(layer_idx) self.forward_funcs.append(layer) self.add_module(name, layer) # TiedLayerSpec objects contain an nn.Module that should be allocated now. elif isinstance(layer, TiedLayerSpec): # Build and register the module if we haven't seen it before. if layer.key not in self.tied_modules: self.tied_modules[layer.key] = layer.build() self.tied_weight_attrs[layer.key] = layer.tied_weight_attr if layer.forward_fn is None: # Just use forward() self.forward_funcs.append(self.tied_modules[layer.key]) else: # User specified fn with args (module, input) self.forward_funcs.append( partial(layer.forward_fn, self.tied_modules[layer.key])) # LayerSpec objects contain an nn.Module that should be allocated now. elif isinstance(layer, LayerSpec): module = layer.build() name = str(layer_idx) self.forward_funcs.append(module) self.add_module(name, module) # Last option: layer may be a functional (e.g., lambda). We do nothing in # that case and just use it in forward() else: self.forward_funcs.append(layer) # All pipeline parameters should be considered as model parallel in the context # of our FP16 optimizer for p in self.parameters(): p.ds_pipe_replicated = False def _count_layer_params(self): """Count the trainable parameters in individual layers. This routine will only build one layer at a time. Returns: A list of the number of parameters in each layer. """ param_counts = [0] * len(self._layer_specs) for idx, layer in enumerate(self._layer_specs): if isinstance(layer, LayerSpec): l = layer.build() params = filter(lambda p: p.requires_grad, l.parameters()) param_counts[idx] = sum(p.numel() for p in params) elif isinstance(layer, nn.Module): params = filter(lambda p: p.requires_grad, layer.parameters()) param_counts[idx] = sum(p.numel() for p in params) return param_counts def _find_layer_type(self, layername): idxs = [] typeregex = regex.compile(layername, regex.IGNORECASE) for idx, layer in enumerate(self._layer_specs): name = None if isinstance(layer, LayerSpec): name = layer.typename.__name__ elif isinstance(layer, nn.Module): name = layer.__class__.__name__ else: try: name = layer.__name__ except AttributeError: continue if typeregex.search(name): idxs.append(idx) if len(idxs) == 0: raise RuntimeError( f"Partitioning '{layername}' found no valid layers to partition.") return idxs
[docs] def forward(self, forward_input): # We need to offset the seed by the microbatch ID. Save it in a local var to # ensure it is preserved in the closure. Otherwise checkpointed forward funcs # will see a different offset. self.micro_offset += 1 def exec_range_func(start, end): ''' Helper function to be used with checkpoint() Adapted from torch.utils.checkpoint:checkpoint_sequential() ''' local_micro_offset = self.micro_offset + 1 def exec_func(*inputs): # Single tensor inputs need to be unwrapped if len(inputs) == 1: inputs = inputs[0] for idx, layer in enumerate(self.forward_funcs[start:end]): self.curr_layer = idx + self._local_start if self.seed_layers: new_seed = (self.base_seed * local_micro_offset) + self.curr_layer if self.seed_fn: self.seed_fn(new_seed) else: ds_utils.set_random_seed(new_seed) inputs = layer(inputs) return inputs return exec_func if self.activation_checkpoint_interval == 0: func = exec_range_func(0, len(self.forward_funcs)) x = func(forward_input) else: num_layers = len(self.forward_funcs) x = forward_input for start_idx in range(0, num_layers, self.activation_checkpoint_interval): end_idx = min(start_idx + self.activation_checkpoint_interval, num_layers) funcs = self.forward_funcs[start_idx:end_idx] # Since we either pass tensors or tuples of tensors without unpacking, we # need to be careful not to double-wrap tensors with tuple. if not isinstance(x, tuple): x = (x, ) if self._is_checkpointable(funcs): x = self.activation_checkpoint_func( exec_range_func(start_idx, end_idx), *x) else: x = exec_range_func(start_idx, end_idx)(*x) return x
def _partition_layers(self, method='uniform'): num_stages = self._topo.get_dim('pipe') stage_id = self._topo.get_coord(self.global_rank).pipe if self.global_rank == 0: logger.info(f'Partitioning pipeline stages with method {method}') method = method.lower() # Each stage gets a simple uniform number of layers. if method == 'uniform': num_layers = len(self._layer_specs) self.parts = ds_utils.partition_uniform(num_items=num_layers, num_parts=num_stages) elif method == 'parameters': param_counts = self._count_layer_params() self.parts = ds_utils.partition_balanced(weights=param_counts, num_parts=num_stages) elif method.startswith('type:'): layertype = method.split(':')[1] binary_weights = [0] * len(self._layer_specs) for idx in self._find_layer_type(layertype): binary_weights[idx] = 1 self.parts = ds_utils.partition_balanced(weights=binary_weights, num_parts=num_stages) elif method == 'profile': raise NotImplementedError(f'Partitioning method {method} not implemented.') else: raise NotImplementedError(f'Partitioning method {method} not implemented.') # Print some information on the partitioning. if self.global_rank == 0: for stage in range(num_stages): start = self.parts[stage] stop = self.parts[stage + 1] print(f'stage={stage} layers={stop - start}') for idx, layer in enumerate(self._layer_specs[start:stop]): name = str(layer) if isinstance(layer, LayerSpec): name = layer.typename.__name__ if isinstance(layer, nn.Module): name = layer.__class__.__name__ else: try: name = layer.__name__ except AttributeError: pass print(f' {idx+start:2d}: {name}') if self.loss_fn: try: print(f' loss: {self.loss_fn.__name__}') except AttributeError: print(f' loss: {self.loss_fn.__class__.__name__}') self._set_bounds(start=self.parts[stage_id], stop=self.parts[stage_id + 1])
[docs] def allreduce_tied_weight_gradients(self): '''All reduce the gradients of the tied weights between tied stages''' for key, comm in self.tied_comms.items(): weight = getattr(self.tied_modules[key], comm['weight_attr']) dist.all_reduce(weight.grad, group=comm['group'])
def _synchronize_tied_weights(self): for key, comm in self.tied_comms.items(): dist.broadcast( getattr(comm['module'], comm['weight_attr']), src=min(comm['ranks']), group=comm['group'], ) def _index_tied_modules(self): ''' Build communication structures for tied modules. ''' tied_comms = {} if self._topo.get_dim('pipe') == 1: return tied_comms specs = self._layer_specs tie_keys = set(s.key for s in specs if isinstance(s, TiedLayerSpec)) for key in tie_keys: # Find the layers that the tied module appears in tied_layers = [] for idx, layer in enumerate(specs): if isinstance(layer, TiedLayerSpec) and layer.key == key: tied_layers.append(idx) # Find all stages with this tied module # TODO: Would be nice to remove the nested data/model parallelism loops and # TODO: instead generalize in some way, since we really just care about the # TODO: stage that owns the tied layer. Then loop over each (dp, mp, ...) # TODO: fiber to generate process groups. tied_stages = set(self.stage_owner(idx) for idx in tied_layers) for dp in range(self._grid.data_parallel_size): for mp in range(self._grid.get_slice_parallel_world_size()): tied_ranks = [] for s in sorted(tied_stages): if self._grid.get_slice_parallel_world_size() > 1: tied_ranks.append( self._grid.stage_to_global(stage_id=s, data=dp, model=mp)) else: tied_ranks.append( self._grid.stage_to_global(stage_id=s, data=dp)) group = dist.new_group(ranks=tied_ranks) # Record this tied module if we own a local copy of it. if self.global_rank in tied_ranks: assert key in self.tied_modules if key in self.tied_modules: tied_comms[key] = { 'ranks': tied_ranks, 'group': group, 'weight_attr': self.tied_weight_attrs[key], 'module': self.tied_modules[key], } # Only count the tied module once in the eyes of the FP16 optimizer if self.global_rank != tied_ranks[0]: for p in self.tied_modules[key].parameters(): p.ds_pipe_replicated = True ''' if len(tied_comms) > 0: print(f'RANK={self.global_rank} tied_comms={tied_comms}') ''' return tied_comms def partitions(self): return self.parts def stage_owner(self, layer_idx): assert 0 <= layer_idx < self._num_layers for stage in range(self._topo.get_dim('pipe')): if self.parts[stage] <= layer_idx < self.parts[stage + 1]: return stage raise RuntimeError(f'Layer {layer_idx} not owned? parts={self.parts}') def _set_bounds(self, start=None, stop=None): """Manually define the range of layers that will be built on this process. These boundaries are treated as list slices and so start is inclusive and stop is exclusive. The default of None for both results in all layers being built locally. """ self._local_start = start self._local_stop = stop def set_checkpoint_interval(self, interval): assert interval >= 0 self.checkpoint_interval = interval
[docs] def topology(self): """ ProcessTopology object to query process mappings. """ return self._topo
def mpu(self): return self._grid def num_pipeline_stages(self): return self._topo.get_dim('pipe')
[docs] def ckpt_prefix(self, checkpoints_path, tag): """Build a prefix for all checkpoint files written by this module. """ # All checkpoint files start with this rank_name = 'module' # Data parallelism is omitted from the naming convention because we are agnostic # to this in the checkpoint. omit_dims = frozenset(['data']) axes = [a for a in self._grid._topo.get_axis_names() if a not in omit_dims] for dim in axes: rank = getattr(self._grid._topo.get_coord(rank=self.global_rank), dim) rank_name += f'-{dim}_{rank:02d}' ckpt_name = os.path.join(checkpoints_path, str(tag), rank_name) return ckpt_name
[docs] def ckpt_layer_path(self, ckpt_dir, local_layer_idx): """Customize a prefix for a specific pipeline module layer. """ idx = local_layer_idx + self._local_start layer_ckpt_path = os.path.join(ckpt_dir, f'layer_{idx:02d}') rank_repr = self._grid._topo.get_rank_repr(rank=self.global_rank) if rank_repr != '': layer_ckpt_path += f'-{rank_repr}' layer_ckpt_path += '-model_states.pt' return layer_ckpt_path
[docs] def ckpt_layer_path_list(self, ckpt_dir, local_layer_idx): """Get all ckpt file list for a specific pipeline module layer. """ idx = local_layer_idx + self._local_start layer_ckpt_path = os.path.join(ckpt_dir, f'layer_{idx:02d}-') layer_ckpt_path += "*model_states.pt" ckpt_files = glob.glob(layer_ckpt_path) ckpt_files.sort() return ckpt_files
def save_state_dict(self, save_dir): if self._grid.data_parallel_id != 0: return os.makedirs(save_dir, exist_ok=True) layer_offset = self._local_start for idx, layer in enumerate(self.forward_funcs): model_ckpt_path = self.ckpt_layer_path(save_dir, idx) if not hasattr(layer, 'state_dict'): continue # We pass cloned tensors to torch.save() to avoid checkpoint bloat which occurs because torch.save() # saves the underlying storage rather than the slice of the storage corresponding to individual tensors. # This is a problem in DeepSpeed because we often allocate tensors using slices of large flattened buffers. # Tensor cloning helps to avoid this problem because the storage of cloned tensors are closer to the true size. # It is expected that the garbage collector will reclaim the cloned tensor storage to avoid memory bloat. # See https://pytorch.org/docs/stable/notes/serialization.html#preserve-storage-sharing orig_state_dict = layer.state_dict() final_state_dict = type(orig_state_dict)( {k: v.clone() for k, v in orig_state_dict.items()}) torch.save(final_state_dict, model_ckpt_path) def load_state_dir(self, load_dir, strict=True): for idx, layer in enumerate(self.forward_funcs): # Functions, etc. will not have state_dicts if not hasattr(layer, 'load_state_dict'): continue # get all checkpoint files for the layer. model_ckpt_list = self.ckpt_layer_path_list(load_dir, idx) mp_rank = self._grid.get_slice_parallel_rank() mp_world_size = self._grid.get_slice_parallel_world_size() sd_loader = SDLoaderFactory.get_sd_loader(model_ckpt_list, version=2.0) load_path, checkpoint, _ = sd_loader.load(mp_world_size, mp_rank, module_key=None, is_pipe_parallel=True) layer.load_state_dict(checkpoint) # if self._grid.data_parallel_id == 0: # logger.info( # f'RANK={self.global_rank} Loaded layer={idx+self._local_start} file={load_path}' # ) self._synchronize_tied_weights() def _is_checkpointable(self, funcs): # This is an unfortunate hack related to torch and deepspeed activation checkpoint implementations. # Some layers like torch.nn.Embedding will not receive grads if checkpointed, which breaks things. # I presume it's related to the discrete inputs that cannot require_grad? Need to revisit. if self.__class__.__name__ in ('GPTModelPipe', 'GPT2ModelPipe'): return all('ParallelTransformerLayerPipe' in f.__class__.__name__ for f in funcs) if self.checkpointable_layers is not None: return all(f.__class__.__name__ in self.checkpointable_layers for f in funcs) params = [f.parameters() for f in funcs if isinstance(f, torch.nn.Module)] return any(len(list(p)) > 0 for p in params)