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tf.nn.safe_embedding_lookup_sparse

Lookup embedding results, accounting for invalid IDs and empty features.

tf.nn.safe_embedding_lookup_sparse(
    embedding_weights, sparse_ids, sparse_weights=None, combiner='mean',
    default_id=None, max_norm=None, name=None
)

The partitioned embedding in embedding_weights must all be the same shape except for the first dimension. The first dimension is allowed to vary as the vocabulary size is not necessarily a multiple of num of shards.

Invalid IDs (< 0) are pruned from input IDs and weights, as well as any IDs with non-positive weight. For an entry with no features, the embedding vector for default_id is returned, or the 0-vector if default_id is not supplied.

The ids and weights may be multi-dimensional. Embeddings are always aggregated along the last dimension.

If len(embedding_weights) > 1, each element id of ids is partitioned between the elements of embedding_weights according to the "div" partition strategy, which means we assign ids to partitions in a contiguous manner. For instance, 13 ids are split across 5 partitions as: [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10], [11, 12]].

If the id space does not evenly divide the number of partitions, each of the first (max_id + 1) % len(embedding_weights) partitions will be assigned one more id.

Args
`embedding_weights`	A single tensor representing the complete embedding tensor, or a list of tensors all of same shape except for the first dimension, representing sharded embedding tensors following "div" partition strategy.
`sparse_ids`	`SparseTensor` of shape `[d_0, d_1, ..., d_n]` containing the ids. `d_0` is typically batch size.
`sparse_weights`	`SparseTensor` of same shape as `sparse_ids`, containing float weights corresponding to `sparse_ids`, or `None` if all weights are be assumed to be 1.0.
`combiner`	A string specifying how to combine embedding results for each entry. Currently "mean", "sqrtn" and "sum" are supported, with "mean" the default.
`default_id`	The id to use for an entry with no features. Defaults to 0-vector.
`max_norm`	If not `None`, all embeddings are l2-normalized to max_norm before combining.
`name`	A name for this operation (optional).

Returns

Returns
A dense tensor representing the combined embeddings for the sparse ids. For each row in the dense tensor represented by `sparse_ids`, the op looks up the embeddings for all ids in that row, multiplies them by the corresponding weight, and combines these embeddings as specified. In other words, if `shape(combined embedding_weights) = [p0, p1, ..., pm]` and `shape(sparse_ids) = shape(sparse_weights) = [d0, d1, ..., dn]` then `shape(output) = [d0, d1, ... dn-1, p1, ..., pm]`. For instance, if params is a 10x20 matrix, and sp_ids / sp_weights are [0, 0]: id 1, weight 2.0 [0, 1]: id 3, weight 0.5 [1, 0]: id -1, weight 1.0 [2, 3]: id 1, weight 3.0 `default_id` is 0. with `combiner`="mean", then the output will be a 3x20 matrix where output[0, :] = (params[1, :] * 2.0 + params[3, :] * 0.5) / (2.0 + 0.5) output[1, :] = (params[0, :] * 1.0) / 1.0 output[2, :] = (params[1, :] * 3.0) / 3.0

A dense tensor representing the combined embeddings for the sparse ids. For each row in the dense tensor represented by sparse_ids, the op looks up the embeddings for all ids in that row, multiplies them by the corresponding weight, and combines these embeddings as specified.

In other words, if

shape(combined embedding_weights) = [p0, p1, ..., pm]

and

shape(sparse_ids) = shape(sparse_weights) = [d0, d1, ..., dn]

then

shape(output) = [d0, d1, ... dn-1, p1, ..., pm].

For instance, if params is a 10x20 matrix, and sp_ids / sp_weights are

[0, 0]: id 1, weight 2.0
[0, 1]: id 3, weight 0.5
[1, 0]: id -1, weight 1.0
[2, 3]: id 1, weight 3.0

default_id is 0.

with combiner="mean", then the output will be a 3x20 matrix where

output[0, :] = (params[1, :] * 2.0 + params[3, :] * 0.5) / (2.0 + 0.5)
output[1, :] = (params[0, :] * 1.0) / 1.0
output[2, :] = (params[1, :] * 3.0) / 3.0

Raises
`ValueError`	if `embedding_weights` is empty.

© 2020 The TensorFlow Authors. All rights reserved.
Licensed under the Creative Commons Attribution License 3.0.
Code samples licensed under the Apache 2.0 License.
https://www.tensorflow.org/versions/r2.3/api_docs/python/tf/nn/safe_embedding_lookup_sparse