from torch.nn.parallel import DataParallel
import torch
from torch.nn.parallel._functions import Scatter
from torch.nn.parallel.parallel_apply import parallel_apply
def scatter(inputs, target_gpus, chunk_sizes, dim=0):
r"""
Slices tensors into approximately equal chunks and
distributes them across given GPUs. Duplicates
references to objects that are not tensors.
"""
def scatter_map(obj):
if isinstance(obj, torch.Tensor):
try:
return Scatter.apply(target_gpus, chunk_sizes, dim, obj)
except:
print("obj", obj.size())
print("dim", dim)
print("chunk_sizes", chunk_sizes)
quit()
if isinstance(obj, tuple) and len(obj) > 0:
return list(zip(*map(scatter_map, obj)))
if isinstance(obj, list) and len(obj) > 0:
return list(map(list, zip(*map(scatter_map, obj))))
if isinstance(obj, dict) and len(obj) > 0:
return list(map(type(obj), zip(*map(scatter_map, obj.items()))))
return [obj for targets in target_gpus]
# After scatter_map is called, a scatter_map cell will exist. This cell
# has a reference to the actual function scatter_map, which has references
# to a closure that has a reference to the scatter_map cell (because the
# fn is recursive). To avoid this reference cycle, we set the function to
# None, clearing the cell
try:
return scatter_map(inputs)
finally:
scatter_map = None
def scatter_kwargs(inputs, kwargs, target_gpus, chunk_sizes, dim=0):
r"""Scatter with support for kwargs dictionary"""
inputs = scatter(inputs, target_gpus, chunk_sizes, dim) if inputs else []
kwargs = scatter(kwargs, target_gpus, chunk_sizes, dim) if kwargs else []
if len(inputs) < len(kwargs):
inputs.extend([() for _ in range(len(kwargs) - len(inputs))])
elif len(kwargs) < len(inputs):
kwargs.extend([{} for _ in range(len(inputs) - len(kwargs))])
inputs = tuple(inputs)
kwargs = tuple(kwargs)
return inputs, kwargs
[docs]class BalancedDataParallel(DataParallel):
""" This class is used to replace the original pytorch DataParallel and balance the first GPU memory usage.
The original script is from: https://github.com/kimiyoung/transformer-xl/blob/master/pytorch/utils/data_parallel.py
"""
def __init__(self, gpu0_bsz, *args, **kwargs):
self.gpu0_bsz = gpu0_bsz
super().__init__(*args, **kwargs)
def forward(self, *inputs, **kwargs):
if not self.device_ids:
return self.module(*inputs, **kwargs)
if self.gpu0_bsz == 0:
device_ids = self.device_ids[1:]
else:
device_ids = self.device_ids
inputs, kwargs = self.scatter(inputs, kwargs, device_ids)
# print('len(inputs)1: ', str(len(inputs)))
# print('self.device_ids[:len(inputs)]', str(self.device_ids[:len(inputs)]))
if len(self.device_ids) == 1:
return self.module(*inputs[0], **kwargs[0])
replicas = self.replicate(self.module, self.device_ids[: len(inputs)])
if self.gpu0_bsz == 0:
replicas = replicas[1:]
outputs = self.parallel_apply(replicas, device_ids, inputs, kwargs)
return self.gather(outputs, self.output_device)
def parallel_apply(self, replicas, device_ids, inputs, kwargs):
return parallel_apply(replicas, inputs, kwargs, device_ids[: len(inputs)])
def scatter(self, inputs, kwargs, device_ids):
bsz = inputs[0].size(self.dim)
num_dev = len(self.device_ids)
gpu0_bsz = self.gpu0_bsz
bsz_unit = (bsz - gpu0_bsz) // (num_dev - 1)
if gpu0_bsz < bsz_unit:
chunk_sizes = [gpu0_bsz] + [bsz_unit] * (num_dev - 1)
delta = bsz - sum(chunk_sizes)
for i in range(delta):
chunk_sizes[i + 1] += 1
if gpu0_bsz == 0:
chunk_sizes = chunk_sizes[1:]
else:
return super().scatter(inputs, kwargs, device_ids)
# print('bsz: ', bsz)
# print('num_dev: ', num_dev)
# print('gpu0_bsz: ', gpu0_bsz)
# print('bsz_unit: ', bsz_unit)
# print('chunk_sizes: ', chunk_sizes)
return scatter_kwargs(inputs, kwargs, device_ids, chunk_sizes, dim=self.dim)