embedding_lookup(params, ids, partition_strategy='mod', name=None, validate_indices=True, max_norm=None)
Looks up `ids` in a list of embedding tensors.
This function is used to perform parallel lookups on the list of
tensors in `params`. It is a generalization of
@{tf.gather}, where `params` is
interpreted as a partitioning of a large embedding tensor. `params` may be
a `PartitionedVariable` as returned by using `tf.get_variable()` with a
partitioner.
If `len(params) > 1`, each element `id` of `ids` is partitioned between
the elements of `params` according to the `partition_strategy`.
In all strategies, if the id space does not evenly divide the number of
partitions, each of the first `(max_id + 1) % len(params)` partitions will
be assigned one more id.
If `partition_strategy` is `"mod"`, we assign each id to partition
`p = id % len(params)`. For instance,
13 ids are split across 5 partitions as:
`[[0, 5, 10], [1, 6, 11], [2, 7, 12], [3, 8], [4, 9]]`
If `partition_strategy` is `"div"`, we assign ids to partitions in a
contiguous manner. In this case, 13 ids are split across 5 partitions as:
`[[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10], [11, 12]]`
The results of the lookup are concatenated into a dense
tensor. The returned tensor has shape `shape(ids) + shape(params)[1:]`.
Args:
params: A single tensor representing the complete embedding tensor,
or a list of P tensors all of same shape except for the first dimension,
representing sharded embedding tensors. Alternatively, a
`PartitionedVariable`, created by partitioning along dimension 0. Each
element must be appropriately sized for the given `partition_strategy`.
ids: A `Tensor` with type `int32` or `int64` containing the ids to be looked
up in `params`.
partition_strategy: A string specifying the partitioning strategy, relevant
if `len(params) > 1`. Currently `"div"` and `"mod"` are supported. Default
is `"mod"`.
name: A name for the operation (optional).
validate_indices: DEPRECATED. If this operation is assigned to CPU, values
in `indices` are always validated to be within range. If assigned to GPU,
out-of-bound indices result in safe but unspecified behavior, which may
include raising an error.
max_norm: If provided, embedding values are l2-normalized to the value of
max_norm.
Returns:
A `Tensor` with the same type as the tensors in `params`.
Raises:
ValueError: If `params` is empty.
embedding_lookup(params, ids)其实就是按照ids顺序返回params中的第ids行。
比如说，ids=[1,3,2],就是返回params中第1,3,2行。返回结果为由params的1,3,2行组成的tensor.
最近在看，一起学习。
比如说，ids=[1,3,2],就是返回params中第1,3,2行。返回结果为由params的1,3,2行组成的tensor.
最近在看，一起学习。
# -*- coding= utf-8 -*-
import tensorflow as tf
import numpy as np
a = [[0.1, 0.2, 0.3], [1.1, 1.2, 1.3], [2.1, 2.2, 2.3], [3.1, 3.2, 3.3], [4.1, 4.2, 4.3]]
a = np.asarray(a)
idx1 = tf.Variable([0, 2, 3, 1], tf.int32)
idx2 = tf.Variable([[0, 2, 3, 1], [4, 0, 2, 2]], tf.int32)
out1 = tf.nn.embedding_lookup(a, idx1)
out2 = tf.nn.embedding_lookup(a, idx2)
init = tf.global_variables_initializer()
with tf.Session() as sess:
sess.run(init)
print sess.run(out1)
print out1
print '=================='
print sess.run(out2)
print out2
输出：
[[ 0.1 0.2 0.3]
[ 2.1 2.2 2.3]
[ 3.1 3.2 3.3]
[ 1.1 1.2 1.3]]
Tensor("embedding_lookup:0", shape=(4, 3), dtype=float64)
==================
[[[ 0.1 0.2 0.3]
[ 2.1 2.2 2.3]
[ 3.1 3.2 3.3]
[ 1.1 1.2 1.3]]
[[ 4.1 4.2 4.3]
[ 0.1 0.2 0.3]
[ 2.1 2.2 2.3]
[ 2.1 2.2 2.3]]]
Tensor("embedding_lookup_1:0", shape=(2, 4, 3), dtype=float64)
