File size: 4,262 Bytes
a93e458 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 |
"""Utility functions used throughout Megatron core"""
from functools import reduce
import operator
import torch
from megatron.core import parallel_state
def ensure_divisibility(numerator, denominator):
"""Ensure that numerator is divisible by the denominator."""
assert numerator % denominator == 0, "{} is not divisible by {}".format(
numerator, denominator
)
def divide(numerator, denominator):
"""Ensure that numerator is divisible by the denominator and return
the division value."""
ensure_divisibility(numerator, denominator)
return numerator // denominator
class GlobalMemoryBuffer:
"""Global buffer to avoid dynamic memory allocations.
Caller should ensure that buffers of the same name
are not used concurrently."""
def __init__(self):
self.buffer = {}
def get_tensor(self, tensor_shape, dtype, name):
required_len = reduce(operator.mul, tensor_shape, 1)
if self.buffer.get((name, dtype), None) is None or \
self.buffer[(name, dtype)].numel() < required_len:
self.buffer[(name, dtype)] = \
torch.empty(required_len,
dtype=dtype,
device=torch.cuda.current_device(),
requires_grad=False)
return self.buffer[(name, dtype)][0:required_len].view(*tensor_shape)
def _kernel_make_viewless_tensor(inp, requires_grad):
'''Make a viewless tensor.
View tensors have the undesirable side-affect of retaining a reference
to the originally-viewed tensor, even after manually setting the '.data'
field. This method creates a new tensor that links to the old tensor's
data, without linking the viewed tensor, referenced via the '._base'
field.
'''
out = torch.empty(
(1,),
dtype = inp.dtype,
device = inp.device,
requires_grad = requires_grad,
)
out.data = inp.data
return out
class MakeViewlessTensor(torch.autograd.Function):
'''
Autograd function to make a viewless tensor.
This function should be used in cases where the computation graph needs
to be propagated, but we only want a viewless tensor (e.g.,
ParallelTransformer's hidden_states). Call this function by passing
'keep_graph = True' to 'make_viewless_tensor()'.
'''
@staticmethod
def forward(ctx, inp, requires_grad):
return _kernel_make_viewless_tensor(inp, requires_grad)
@staticmethod
def backward(ctx, grad_output):
return grad_output, None
def make_viewless_tensor(inp, requires_grad, keep_graph):
'''
Entry-point for creating viewless tensors.
This method should be used, rather than calling 'MakeViewlessTensor'
or '_kernel_make_viewless_tensor' directly. This method acts as a
switch for determining if an autograd function or a regular method
should be used to create the tensor.
'''
# return tensor as-is, if not a 'view'
if inp._base is None:
return inp
# create viewless tensor
if keep_graph:
return MakeViewlessTensor.apply(inp, requires_grad)
else:
return _kernel_make_viewless_tensor(inp, requires_grad)
def assert_viewless_tensor(tensor, extra_msg = None):
'''Assert that a tensor is not a view (i.e., its '._base' field is
not set).'''
if isinstance(tensor, list):
[ assert_viewless_tensor(t) for t in tensor ]
return tensor
if not isinstance(tensor, torch.Tensor):
return tensor
assert tensor._base is None, (
"Ensure tensor._base is None before setting tensor.data or storing "
"tensor to memory buffer. Otherwise, a memory leak will occur (and "
"likely accumulate over iterations). %s"
) % extra_msg
return tensor
def safely_set_viewless_tensor_data(tensor, new_data_tensor):
'''Safely set tensor's '.data' field.
Check first that the tensor is viewless (i.e., '._base' not set). If not,
raise an exception.
'''
assert_viewless_tensor(tensor, extra_msg = "FYI, tensor._base has shape %s, and new_data_tensor has shape %s." % ("--" if tensor._base is None else tensor._base.shape, new_data_tensor.shape))
tensor.data = new_data_tensor
|