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Original file line number Diff line number Diff line change
@@ -0,0 +1,184 @@
.. {#openvino_docs_ops_sparse_EmbeddingBagOffsets_15}

EmbeddingBagOffsets
======================


.. meta::
:description: Learn about EmbeddingBagOffsets-15 - a sparse operation, which
can be performed on three required and two optional input tensors.

**Versioned name**: *EmbeddingBagOffsets-15*

**Category**: *Sparse*

**Short description**: Computes sums or means of "bags" of embeddings, without instantiating the intermediate embeddings.

**Detailed description**:

Operation EmbeddingBagOffsets is an implementation of ``torch.nn.EmbeddingBag`` with indices and offsets inputs being 1D tensors.

For each index in ``indices`` this operator gathers values from ``emb_table`` embedding table. Then values at indices in the range of the same bag (based on ``offset`` input) are reduced according to ``reduction`` attribute.

Values in ``offsets`` define starting index in ``indices`` tensor of each "bag",
e.g. ``offsets`` with value ``[0, 3, 4, 4, 6]`` define 5 "bags" containing ``[3, 1, 0, 2, num_indices-6]`` elements corresponding to ``[indices[0:3], indices[3:4], empty_bag, indices[4:6], indices[6:]]`` slices of indices per bag.

EmbeddingBagOffsets is an equivalent to following NumPy snippet:

.. code-block:: py

def embedding_bag_offsets(
emb_table: np.ndarray,
indices: np.ndarray,
offsets: np.ndarray,
default_index: Optional[int] = None,
per_sample_weights: Optional[np.ndarray] = None,
reduction: Literal["sum", "mean"] = "sum",
):
assert (
reduction == "sum" or per_sample_weights is None
), "Attribute per_sample_weights is only supported in sum reduction."
if per_sample_weights is None:
per_sample_weights = np.ones_like(indices)
embeddings = []
for emb_idx, emb_weight in zip(indices, per_sample_weights):
embeddings.append(emb_table[emb_idx] * emb_weight)
previous_offset = offsets[0]
bags = []
offsets = np.append(offsets, len(indices))
for bag_offset in offsets[1:]:
bag_size = bag_offset - previous_offset
if bag_size != 0:
embedding_bag = embeddings[previous_offset:bag_offset]
reduced_bag = np.add.reduce(embedding_bag)
if reduction == "mean":
reduced_bag = reduced_bag / bag_size
bags.append(reduced_bag)
else:
# Empty bag case
if default_index is not None and default_index != -1:
bags.append(emb_table[default_index])
else:
bags.append(np.zeros(emb_table.shape[1:]))
previous_offset = bag_offset
return np.stack(bags, axis=0)


**Attributes**:

* *reduction*

* **Description**: reduction mode.
* **Range of values**:

* sum - compute weighted sum, using corresponding values of ``per_sample_weights`` as weights if provided.
* mean - compute average of values in bag. Input ``per_sample_weights`` is not supported and will raise exception.

* **Type**: ``string``
* **Default value**: sum
* **Required**: *no*

**Inputs**:

* **1**: ``emb_table`` tensor containing the embedding lookup table of the module of shape ``[num_emb, emb_dim1, emb_dim2, ...]`` and of type *T*. **Required.**
* **2**: ``indices`` tensor of shape ``[num_indices]`` and of type *T_IND*. **Required.**
* **3**: ``offsets`` tensor of shape ``[batch]`` and of type *T_IND* containing the starting index positions of each "bag" in ``indices``. Maximum value of offsets cannot be greater than length of ``indices``. **Required.**
* **4**: ``default_index`` scalar of type *T_IND* containing default index in embedding table to fill empty "bags". If set to ``-1`` or not provided, empty "bags" are filled with zeros. Reverse indexing using negative values is not supported. **Optional.**
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Usage of -1 is not an ideal solution, but as we discussed it's aligned with current behavior of some plugins and it resolves the empty bags issues. Although the main reason of adding v15 version was enablement of the "mean" mode, great to see the clarification of the default_index behavior as well.

* **5**: ``per_sample_weights`` tensor of the same shape as ``indices`` and of type *T*. Supported only when *reduction* attribute is set to ``"sum"``. Each value in this tensor are multiplied with each value pooled from embedding table for each index. Optional, default is tensor of ones. **Optional.**

**Outputs**:

* **1**: tensor of shape ``[batch, emb_dim1, emb_dim2, ...]`` and of type *T* containing embeddings for each bag.

**Types**

* *T*: any numeric type.
* *T_IND*: ``int32`` or ``int64``.

**Example**

*Example 1: per_sample_weights are provided, default_index is set to 0 to fill empty bag with values gathered form emb_table on given index.*

.. code-block:: xml

<layer ... type="EmbeddingBagOffsets" ... >
<data reduction="sum"/>
<input>
<port id="0"> <!-- emb_table value is: [[-0.2, -0.6], [-0.1, -0.4], [-1.9, -1.8], [-1., 1.5], [ 0.8, -0.7]] -->
<dim>5</dim>
<dim>2</dim>
</port>
<port id="1"> <!-- indices value is: [0, 2, 3, 4] -->
<dim>4</dim>
</port>
<port id="2"> <!-- offsets value is: [0, 2, 2] - 3 "bags" containing [2,0,4-2] elements, second "bag" is empty -->
<dim>3</dim>
</port>
<port id="3"/> <!-- default_index value is: 0 -->
<port id="4"/> <!-- per_sample_weights value is: [0.5, 0.5, 0.5, 0.5] -->
<dim>4</dim>
</port>
</input>
<output>
<port id="5"> <!-- output value is: [[-1.05, -1.2], [-0.2, -0.6], [-0.1, 0.4]] -->
<dim>3</dim>
<dim>2</dim>
</port>
</output>
</layer>

*Example 2: per_sample_weights are provided, default_index is set to -1 to fill empty bag with 0.*

.. code-block:: xml

<layer ... type="EmbeddingBagOffsets" ... >
<data reduction="sum"/>
<input>
<port id="0"> <!-- emb_table value is: [[-0.2, -0.6], [-0.1, -0.4], [-1.9, -1.8], [-1., 1.5], [ 0.8, -0.7]] -->
<dim>5</dim>
<dim>2</dim>
</port>
<port id="1"> <!-- indices value is: [0, 2, 3, 4] -->
<dim>4</dim>
</port>
<port id="2"> <!-- offsets value is: [0, 2, 2] - 3 "bags" containing [2,0,4-2] elements, second "bag" is empty -->
<dim>3</dim>
</port>
<port id="3"/> <!-- default_index value is: -1 - fill empty bag with 0-->
<port id="4"/> <!-- per_sample_weights value is: [0.5, 0.2, -2, 1] -->
<dim>4</dim>
</port>
</input>
<output>
<port id="5"> <!-- output value is: [[-0.48, -0.66], [0., 0.], [2.8, -3.7]] -->
<dim>3</dim>
<dim>2</dim>
</port>
</output>
</layer>

*Example 3: Example of reduction set to mean.*

.. code-block:: xml

<layer ... type="EmbeddingBagOffsets" ... >
<data reduction="mean"/>
<input>
<port id="0"> <!-- emb_table value is: [[-0.2, -0.6], [-0.1, -0.4], [-1.9, -1.8], [-1., 1.5], [ 0.8, -0.7]] -->
<dim>5</dim>
<dim>2</dim>
</port>
<port id="1"> <!-- indices value is: [0, 2, 3, 4] -->
<dim>4</dim>
</port>
<port id="2"> <!-- offsets value is: [0, 2, 2] - 3 "bags" containing [2,0,4-2] elements, second "bag" is empty -->
<dim>3</dim>
</port>
</input>
<output>
<port id="3"> <!-- output value is: [[-1.05, -1.2], [0., 0.], [-0.1, 0.4]] -->
<dim>3</dim>
<dim>2</dim>
</port>
</output>
</layer>
Original file line number Diff line number Diff line change
Expand Up @@ -14,15 +14,56 @@ EmbeddingBagOffsetsSum

**Short description**: Computes sums of "bags" of embeddings, without instantiating the intermediate embeddings.

**Detailed description**: This is the second case of the PyTorch `EmbeddingBag <https://pytorch.org/docs/stable/nn.html#embeddingbag>`__ , it has indices in two 1D tensors provided as 2nd and 3rd inputs. For each index in ``indices`` this operator gets values from ``data`` embedding table and sums all values belonging to each bag. Values in ``offsets`` define starting index in ``indices`` tensor of each "bag", e.g. ``offsets`` with value ``[0,3,4,4,6]`` define 5 "bags" containing ``[3,1,0,2,n-6]`` elements.
**Detailed description**:

Operation EmbeddingBagOffsets is an implementation of ``torch.nn.EmbeddingBag`` with indices and offsets inputs being 1D tensors.

For each index in ``indices`` this operator gathers values from ``emb_table`` embedding table. Then values at indices in the range of the same bag (based on ``offset`` input) are reduced according to ``reduction`` attribute.

Values in ``offsets`` define starting index in ``indices`` tensor of each "bag",
e.g. ``offsets`` with value ``[0, 3, 4, 4, 6]`` define 5 "bags" containing ``[3, 1, 0, 2, num_indices-6]`` elements corresponding to ``[indices[0:3], indices[3:4], empty_bag, indices[4:6], indices[6:]]`` slices of indices per bag.

EmbeddingBagOffsetsSum is an equivalent to following NumPy snippet:

.. code-block:: py

def embedding_bag_offsets(
emb_table: np.ndarray,
indices: np.ndarray,
offsets: np.ndarray,
default_index: Optional[int] = None,
per_sample_weights: Optional[np.ndarray] = None,
):
if per_sample_weights is None:
per_sample_weights = np.ones_like(indices)
embeddings = []
for emb_idx, emb_weight in zip(indices, per_sample_weights):
embeddings.append(emb_table[emb_idx] * emb_weight)
previous_offset = offsets[0]
bags = []
offsets = np.append(offsets, len(indices))
for bag_offset in offsets[1:]:
bag_size = bag_offset - previous_offset
if bag_size != 0:
embedding_bag = embeddings[previous_offset:bag_offset]
reduced_bag = np.add.reduce(embedding_bag)
bags.append(reduced_bag)
else:
# Empty bag case
if default_index is not None and default_index != -1:
bags.append(emb_table[default_index])
else:
bags.append(np.zeros(emb_table.shape[1:]))
previous_offset = bag_offset
return np.stack(bags, axis=0)

**Attributes**: EmbeddingBagOffsetsSum operation has no attributes.

**Inputs**:

* **1**: ``emb_table`` tensor containing the embedding lookup table of the module of shape ``[num_emb, emb_dim1, emb_dim2, ...]`` and of type *T*. **Required.**
* **2**: ``indices`` tensor of shape ``[num_indices]`` and of type *T_IND*. **Required.**
* **3**: ``offsets`` tensor of shape ``[batch]`` and of type *T_IND* containing the starting index positions of each "bag" in ``indices``. **Required.**
* **3**: ``offsets`` tensor of shape ``[batch]`` and of type *T_IND* containing the starting index positions of each "bag" in ``indices``. Maximum value of offsets cannot be greater than length of ``indices``. **Required.**
* **4**: ``default_index`` scalar of type *T_IND* containing default index in embedding table to fill empty "bags". If set to ``-1`` or not provided, empty "bags" are filled with zeros. Reverse indexing using negative values is not supported. **Optional.**
* **5**: ``per_sample_weights`` tensor of the same shape as ``indices`` and of type *T*. Each value in this tensor are multiplied with each value pooled from embedding table for each index. Optional, default is tensor of ones. **Optional.**

Expand All @@ -37,7 +78,9 @@ EmbeddingBagOffsetsSum

**Example**

.. code-block:: cpp
*Example 1: per_sample_weights are provided, default_index is set to 0 to fill empty bag with values gathered form emb_table on given index.*

.. code-block:: xml

<layer ... type="EmbeddingBagOffsetsSum" ... >
<input>
Expand All @@ -52,7 +95,7 @@ EmbeddingBagOffsetsSum
<dim>3</dim>
</port>
<port id="3"/> <!-- default_index value is: 0 -->
<port id="4"/> <!-- per_sample_weigths value is: [0.5, 0.5, 0.5, 0.5] -->
<port id="4"/> <!-- per_sample_weights value is: [0.5, 0.5, 0.5, 0.5] -->
<dim>4</dim>
</port>
</input>
Expand All @@ -64,4 +107,31 @@ EmbeddingBagOffsetsSum
</output>
</layer>

*Example 2: per_sample_weights are provided, default_index is set to -1 to fill empty bag with 0.*

.. code-block:: xml

<layer ... type="EmbeddingBagOffsets" ... >
<input>
<port id="0"> <!-- emb_table value is: [[-0.2, -0.6], [-0.1, -0.4], [-1.9, -1.8], [-1., 1.5], [ 0.8, -0.7]] -->
<dim>5</dim>
<dim>2</dim>
</port>
<port id="1"> <!-- indices value is: [0, 2, 3, 4] -->
<dim>4</dim>
</port>
<port id="2"> <!-- offsets value is: [0, 2, 2] - 3 "bags" containing [2,0,4-2] elements, second "bag" is empty -->
<dim>3</dim>
</port>
<port id="3"/> <!-- default_index value is: -1 - fill empty bag with 0-->
<port id="4"/> <!-- per_sample_weights value is: [0.5, 0.5, 0.5, 0.5] -->
<dim>4</dim>
</port>
</input>
<output>
<port id="5"> <!-- output value is: [[-1.05, -1.2], [0., 0.], [-0.1, 0.4]] -->
<dim>3</dim>
<dim>2</dim>
</port>
</output>
</layer>
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