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reduce_scatter.py
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reduce_scatter.py
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# Copyright (c) 2022 PaddlePaddle Authors. 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
# limitations under the License.
from paddle.distributed.communication import stream
from paddle.distributed.communication.reduce import ReduceOp
from paddle.distributed.communication.stream.reduce_scatter import (
_reduce_scatter_base as _reduce_scatter_base_stream,
)
def reduce_scatter(
tensor, tensor_list, op=ReduceOp.SUM, group=None, sync_op=True
):
"""
Reduces, then scatters a list of tensors to all processes in a group
Args:
tensor (Tensor): The output tensor on each rank. The result will overwrite this tenor after communication. Support
float16, float32, float64, int32, int64, int8, uint8 or bool as the input data type.
tensor_list (List[Tensor]]): List of tensors to reduce and scatter. Every element in the list must be a Tensor whose data type
should be float16, float32, float64, int32, int64, int8, uint8, bool or bfloat16.
op (ReduceOp.SUM|ReduceOp.MAX|ReduceOp.MIN|ReduceOp.PROD, optional): The reduction used. If none is given, use ReduceOp.SUM as default.
group (Group, optional): Communicate in which group. If none is given, use the global group as default.
sync_op (bool, optional): Indicate whether the communication is sync or not. If none is given, use true as default.
Returns:
Return a task object.
Warning:
This API only supports the dygraph mode.
Examples:
.. code-block:: python
# required: distributed
import paddle
import paddle.distributed as dist
dist.init_parallel_env()
if dist.get_rank() == 0:
data1 = paddle.to_tensor([0, 1])
data2 = paddle.to_tensor([2, 3])
else:
data1 = paddle.to_tensor([4, 5])
data2 = paddle.to_tensor([6, 7])
dist.reduce_scatter(data1, [data1, data2])
print(data1)
# [4, 6] (2 GPUs, out for rank 0)
# [8, 10] (2 GPUs, out for rank 1)
"""
return stream.reduce_scatter(
tensor,
tensor_list,
op=op,
group=group,
sync_op=sync_op,
use_calc_stream=False,
)
def _reduce_scatter_base(
output, input, op=ReduceOp.SUM, group=None, sync_op=True
):
"""
Reduces, then scatters a flattened tensor to all processes in a group.
Args:
output (Tensor): Output tensor. Its data type should be float16, float32, float64, int32, int64, int8, uint8, bool or bfloat16.
input (Tensor): Input tensor that is of size output tensor size times world size. Its data type
should be float16, float32, float64, int32, int64, int8, uint8, bool or bfloat16.
op (ReduceOp.SUM|ReduceOp.MAX|ReduceOp.MIN|ReduceOp.PROD): Optional. The operation used. Default: ReduceOp.SUM.
group (ProcessGroup, optional): The process group to work on. If None,
the default process group will be used.
sync_op (bool, optional): Whether this op is a sync op. The default value is True.
Returns:
Async task handle, if sync_op is set to False.
None, if sync_op or if not part of the group.
Examples:
.. code-block:: python
# required: distributed
import paddle
import paddle.distributed as dist
dist.init_parallel_env()
rank = dist.get_rank()
data = paddle.arange(4) + rank
# [0, 1, 2, 3] (2 GPUs, for rank 0)
# [1, 2, 3, 4] (2 GPUs, for rank 1)
output = paddle.empty(shape=[2], dtype=data.dtype)
dist.collective._reduce_scatter_base(output, data)
print(output)
# [1, 3] (2 GPUs, out for rank 0)
# [5, 7] (2 GPUs, out for rank 1)
"""
return _reduce_scatter_base_stream(
output,
input,
op=op,
group=group,
sync_op=sync_op,
use_calc_stream=False,
)