Source code for horovod.mxnet.compression
# Copyright 2018 Uber Technologies, Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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# ==============================================================================
"""Gradient compression algorithms."""
class Compressor(object):
"""Interface for compressing and decompressing a given tensor."""
@staticmethod
def compress(tensor):
"""Compresses a tensor and returns it with the context needed to decompress it."""
pass
@staticmethod
def decompress(tensor, ctx):
"""Decompress the tensor with the given context."""
pass
class NoneCompressor(Compressor):
"""Default no-op compression."""
@staticmethod
def compress(tensor):
"""Returns the tensor unmodified."""
return tensor, None
@staticmethod
def decompress(tensor, ctx):
"""Returns the tensor unmodified."""
return tensor
class FP16Compressor(Compressor):
"""Compress all floating point gradients to 16-bit."""
@staticmethod
def compress(tensor):
"""Downcasts the tensor to 16-bit."""
tensor_compressed = tensor
if 'float' in str(tensor.dtype):
# Only allow compression from other floating point types
tensor_compressed = tensor.astype('float16', copy=False)
return tensor_compressed, tensor.dtype
@staticmethod
def decompress(tensor, ctx):
"""Upcasts the tensor to the initialization dtype."""
tensor_decompressed = tensor
dtype = ctx
if 'float' in str(dtype):
tensor_decompressed = tensor.astype(dtype, copy=False)
return tensor_decompressed
[docs]class Compression(object):
"""Optional gradient compression algorithm used during allreduce."""
"""Do not compress the gradients. This is the default."""
none = NoneCompressor
"""Compress all floating point gradients to 16-bit."""
fp16 = FP16Compressor