tf.distribute.HierarchicalCopyAllReduce

TensorFlow 1 version View source on GitHub

Reduction using hierarchical copy all-reduce.

tf.distribute.HierarchicalCopyAllReduce(
    num_packs=1
)

It reduces to one GPU along edges in some hierarchy and broadcasts back to each GPU along the same path. Before performing all-reduce, tensors will be repacked or aggregated for more efficient cross-device transportation.

This is a reduction created for Nvidia DGX-1 which assumes GPUs connects like that on DGX-1 machine. If you have different GPU inter-connections, it is likely that it would be slower than tf.distribute.ReductionToOneDevice.

num_packs values will be packed in this many splits. num_packs should be greater than 0.

ValueError if num_packs is zero or negative.

Methods

batch_reduce

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batch_reduce(
    reduce_op, value_destination_pairs
)

Reduce PerReplica objects in a batch.

Reduce each first element in value_destination_pairs to each second element which indicates the destinations.

Args
reduce_op Indicates how per_replica_value will be reduced. Accepted values are tf.distribute.ReduceOp.SUM, tf.distribute.ReduceOp.MEAN.
value_destination_pairs a list or a tuple of tuples of PerReplica objects (or tensors with device set if there is one device) and destinations.

Returns
a list of Mirrored objects.

Raises
ValueError if value_destination_pairs is not a list or a tuple of tuples of PerReplica objects and destinations

broadcast

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broadcast(
    tensor, destinations
)

Broadcast the tensor to destinations.

Args
tensor the tensor to broadcast.
destinations the broadcast destinations.

Returns
a Mirrored object.

reduce

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reduce(
    reduce_op, per_replica_value, destinations
)

Reduce per_replica_value to destinations.

It runs the reduction operation defined by reduce_op and put the result on destinations.

Args
reduce_op Indicates how per_replica_value will be reduced. Accepted values are tf.distribute.ReduceOp.SUM, tf.distribute.ReduceOp.MEAN.
per_replica_value a PerReplica object or a tensor with device set.
destinations the reduction destinations.

Returns
a Mirrored object.

Raises
ValueError if per_replica_value can't be converted to a PerReplica object.