DOCS: ported changes from 2022.1 release branch (#11206)

* Extensibility guide with FE extensions and remove OV_FRAMEWORK_MAP from docs

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* Minor fixes in extension snippets

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* DOCS: transition banner (#10973)

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* update

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* DOCS: fixed hardcoded links  (#11100)

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* refactoring tput/latency sections

* next iteration (mostly latency), also brushed the auto-batching and other sections

* updates sync/async images

* common opts brushed

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* minor brushing of common and auto-batching

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* fixed links

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* Added a note on the batch size

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* [80085] New images for docs (#11114)

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# OpenVINO Extensibility Mechanism {#openvino_docs_Extensibility_UG_Intro}
# OpenVINO Extensibility Mechanism {#openvino_docs_Extensibility_UG_Intro}
@sphinxdirective
@@ -7,41 +7,67 @@
:hidden:
openvino_docs_Extensibility_UG_add_openvino_ops
openvino_docs_Extensibility_UG_Frontend_Extensions
openvino_docs_Extensibility_UG_GPU
openvino_docs_MO_DG_prepare_model_customize_model_optimizer_Customize_Model_Optimizer
@endsphinxdirective
The Intel® Distribution of OpenVINO™ toolkit supports neural network models trained with various frameworks, including
TensorFlow, PyTorch, ONNX, PaddlePaddle, MXNet, Caffe, and Kaldi. The list of supported operations (layers) is different for
TensorFlow, PyTorch, ONNX, PaddlePaddle, MXNet, Caffe, and Kaldi. The list of supported operations is different for
each of the supported frameworks. To see the operations supported by your framework, refer to
[Supported Framework Operations](../MO_DG/prepare_model/Supported_Frameworks_Layers.md).
Custom operations, that is those not included in the list, are not recognized by OpenVINO™ out-of-the-box. Therefore, creating Intermediate Representation (IR) for a model using them requires additional steps. This guide illustrates the workflow for running inference on topologies featuring custom operations, allowing you to plug in your own implementation for existing or completely new operations.
Custom operations, that is those not included in the list, are not recognized by OpenVINO™ out-of-the-box. The need in custom operation may appear in two main cases:
If your model contains operations not normally supported by OpenVINO™, the OpenVINO™ Extensibility API lets you add support for those custom operations and use one implementation for Model Optimizer and OpenVINO™ Runtime.
1. A regular framework operation that is new or rarely used and that’s why hasn’t been supported in OpenVINO yet.
There are two steps to support inference of a model with custom operation(s):
1. Add support for a [custom operation in the Model Optimizer](../MO_DG/prepare_model/customize_model_optimizer/Customize_Model_Optimizer.md) so
the Model Optimizer can generate the IR with the operation.
2. Create a custom operation in it as described in the [Custom Operation](add_openvino_ops.md).
2. A new user operation that was created for some specific model topology by a model author using framework extension capabilities.
## OpenVINO™ Extensions
Importing models with such operations requires additional steps. This guide illustrates the workflow for running inference on models featuring custom operations, allowing you to plug in your own implementation for them. OpenVINO™ Extensibility API lets you add support for those custom operations and use one implementation for Model Optimizer and OpenVINO™ Runtime.
OpenVINO™ provides extensions for:
Defining a new custom operation basically consist of two parts:
* [Custom OpenVINO™ Operation](add_openvino_ops.md):
- Enables the creation of unsupported operations
- Enables the use of `ov::Core::read_model` to read models with unsupported operations
- Provides a shape inference mechanism for custom operations
- Provides an evaluate method that allows you to support the operation on CPU or perform constant folding
* [Model Optimizer Extensibility](../MO_DG/prepare_model/customize_model_optimizer/Customize_Model_Optimizer.md):
- Enables support of new operations to generate IR
- Enables support of custom transformations to replace sub-graphs for performance optimization
1. Definition of operation semantics in OpenVINO, the code that describes how this operation should be inferred consuming input tensor(s) and producing output tensor(s).
> **NOTE**: This documentation is written based on the [Template extension](https://github.com/openvinotoolkit/openvino/tree/master/docs/template_extension/new), which demonstrates extension development details. You can review the complete code, which is fully compilable and up-to-date, to see how it works.
2. Mapping rule that facilitates conversion of framework operation representation to OpenVINO defined operation semantics.
## Load extensions to OpenVINO™ Runtime
The first part is required for inference, the second part is required for successful import of a model containing such operations from the original framework model format. There are several options to implement each part, the next sections will describe them in detail.
## Definition of Operation Semantics
If the custom operation can be mathematically represented as a combination of exiting OpenVINO operations and such decomposition gives desired performance, then low-level operation implementation is not required. When deciding feasibility of such decomposition refer to the latest OpenVINO operation set. You can use any valid combination of exiting operations. How to map a custom operation is described in the next section of this document.
If such decomposition is not possible or appears too bulky with lots of consisting operations that are not performing well, then a new class for the custom operation should be implemented as described in the [Custom Operation Guide](add_openvino_ops.md).
Prefer implementing a custom operation class if you already have a generic C++ implementation of operation kernel. Otherwise try to decompose the operation first as described above and then after verifying correctness of inference and resulting performance, optionally invest to implementing bare metal C++ implementation.
## Mapping from Framework Operation
Depending on model format used for import, mapping of custom operation is implemented differently, choose one of:
1. If model is represented in ONNX (including models exported from Pytorch in ONNX) or PaddlePaddle formats, then one of the classes from [Frontend Extension API](frontend_extensions.md) should be used. It consists of several classes available in C++ which can be used with Model Optimizer `--extensions` option or when model is imported directly to OpenVINO run-time using read_model method. Python API is also available for run-time model importing.
2. If model is represented in TensorFlow, Caffe, Kaldi or MXNet formats, then [Model Optimizer Extensions](../MO_DG/prepare_model/customize_model_optimizer/Customize_Model_Optimizer.md) should be used. This approach is available for model conversion in Model Optimizer only.
Existing of two approaches simultaneously is explained by two different types of frontends used for model conversion in OpenVINO: new frontends (ONNX, PaddlePaddle) and legacy frontends (TensorFlow, Caffe, Kaldi and MXNet). Model Optimizer can use both front-ends in contrast to the direct import of model with `read_model` method which can use new frontends only. Follow one of the appropriate guides referenced above to implement mappings depending on framework frontend.
If you are implementing extensions for ONNX or PaddlePaddle new frontends and plan to use Model Optimizer `--extension` option for model conversion, then the extensions should be
1. Implemented in C++ only
2. Compiled as a separate shared library (see details how to do that later in this guide).
You cannot write new frontend extensions using Python API if you plan to use them with Model Optimizer.
Remaining part of this guide uses Frontend Extension API applicable for new frontends.
## Registering Extensions
A custom operation class and a new mapping frontend extension class object should be registered to be usable in OpenVINO runtime.
> **NOTE**: This documentation is written based on the [Template extension](https://github.com/openvinotoolkit/openvino/tree/master/docs/template_extension/new), which demonstrates extension development details based on minimalistic `Identity` operation that is a placeholder for your real custom operation. You can review the complete code, which is fully compliable, to see how it works.
To load the extensions to the `ov::Core` object, use the `ov::Core::add_extension` method, this method allows to load library with extensions or extensions from the code.
@@ -49,27 +75,50 @@ To load the extensions to the `ov::Core` object, use the `ov::Core::add_extensio
Extensions can be loaded from code with `ov::Core::add_extension` method:
@sphinxtabset
@sphinxtab{C++}
@snippet docs/snippets/ov_extensions.cpp add_extension
@endsphinxtab
@sphinxtab{Python}
@snippet docs/snippets/ov_extensions.py add_extension
@endsphinxtab
@endsphinxtabset
`Identity` is custom operation class defined in [Custom Operation Guide](add_openvino_ops.md). This is enough to enable reading IR which uses `Identity` extension operation emitted by Model Optimizer. To be able to load original model directly to the runtime, you need to add also a mapping extension:
@sphinxdirective
.. tab:: C++
.. doxygensnippet:: docs/snippets/ov_extensions.cpp
:language: cpp
:fragment: add_extension
:fragment: add_frontend_extension
.. tab:: Python
.. doxygensnippet:: docs/snippets/ov_extensions.py
:language: python
:fragment: add_extension
:fragment: add_frontend_extension
@endsphinxdirective
When Python API is used there is no way to implement a custom OpenVINO operation. Also, even if custom OpenVINO operation is implemented in C++ and loaded to the runtime through a shared library, there is still no way to add a frontend mapping extension that refers to this custom operation. Use C++ shared library approach to implement both operations semantics and framework mapping in this case.
You still can use Python for operation mapping and decomposition in case if operations from the standard OpenVINO operation set is used only.
### Create library with extensions
You need to create extension library in following cases:
- Load extensions to Model Optimizer
- Load extensions to Python application
You need to create extension library in the following cases:
- Convert model with custom operations in Model Optimizer
- Load model with custom operations in Python application. It is applicable for both framework model and IR.
- Loading models with custom operations in tools that support loading extensions from a library, for example `benchmark_app`.
If you want to create an extension library, for example in order to load these extensions to the Model Optimizer, you need to do next steps:
Create an entry point for extension library. OpenVINO™ provides an `OPENVINO_CREATE_EXTENSIONS()` macro, which allows to define an entry point to a library with OpenVINO™ Extensions.
@@ -97,24 +146,25 @@ $ cmake --build .
After the build you can use path to your extension library to load your extensions to OpenVINO™ Runtime:
@sphinxdirective
@sphinxtabset
.. tab:: C++
@sphinxtab{C++}
.. doxygensnippet:: docs/snippets/ov_extensions.cpp
:language: cpp
:fragment: add_extension_lib
@snippet docs/snippets/ov_extensions.cpp add_extension_lib
.. tab:: Python
@endsphinxtab
.. doxygensnippet:: docs/snippets/ov_extensions.py
:language: python
:fragment: add_extension_lib
@sphinxtab{Python}
@endsphinxdirective
@snippet docs/snippets/ov_extensions.py add_extension_lib
@endsphinxtab
@endsphinxtabset
## See Also
* [OpenVINO Transformations](./ov_transformations.md)
* [Using Inference Engine Samples](../OV_Runtime_UG/Samples_Overview.md)
* [Using OpenVINO Runtime Samples](../OV_Runtime_UG/Samples_Overview.md)
* [Hello Shape Infer SSD sample](../../samples/cpp/hello_reshape_ssd/README.md)
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# Custom OpenVINO™ Operations {#openvino_docs_Extensibility_UG_add_openvino_ops}
# Custom OpenVINO™ Operations {#openvino_docs_Extensibility_UG_add_openvino_ops}
OpenVINO™ Extension API allows you to register custom operations to support models with operations which OpenVINO™ does not support out-of-the-box.
@@ -20,14 +20,10 @@ Follow the steps below to add a custom operation:
5. Override the `visit_attributes` method, which enables serialization and deserialization of operation attributes. An `AttributeVisitor` is passed to the method, and the implementation is expected to walk over all the attributes in the op using the type-aware `on_attribute` helper. Helpers are already implemented for standard C++ types like `int64_t`, `float`, `bool`, `vector`, and for existing OpenVINO defined types.
6. Override `evaluate`, which is an optional method that enables fallback of some devices to this implementation and the application of constant folding if there is a custom operation on the constant branch. If your operation contains `evaluate` method you also need to override the `has_evaluate` method, this method allow to get information about availability of `evaluate` method for the operation.
7. Add the `OPENVINO_FRAMEWORK_MAP` macro if you want to map custom operation to framework operation with the same name. It is an optional macro which can be used for one to one mapping. In order to use this macro please include frontend specific headers:
@snippet template_extension/new/identity.hpp op:frontend_include
6. Override `evaluate`, which is an optional method that enables fallback of some devices to this implementation and the application of constant folding if there is a custom operation on the constant branch. If your operation contains `evaluate` method you also need to override the `has_evaluate` method, this method allows to get information about availability of `evaluate` method for the operation.
Based on that, declaration of an operation class can look as follows:
@snippet template_extension/new/identity.hpp op:header
### Operation Constructors
@@ -55,8 +51,9 @@ OpenVINO™ operation contains two constructors:
@snippet template_extension/new/identity.cpp op:visit_attributes
### `evaluate()` and `has_evaluate()`
### evaluate() and has_evaluate()
`ov::Node::evaluate` method enables you to apply constant folding to an operation.
@snippet template_extension/new/identity.cpp op:evaluate
@@ -0,0 +1,105 @@
# Frontend Extensions {#openvino_docs_Extensibility_UG_Frontend_Extensions}
The goal of this chapter is to explain how to use Frontend extension classes to facilitate mapping of custom operations from framework model representation to OpenVINO representation. Refer to [Introduction to OpenVINO Extension](Intro.md) to understand entire flow.
This API is applicable for new frontends only, which exist for ONNX and PaddlePaddle. If a different model format is used, follow legacy [Model Optimizer Extensions](../MO_DG/prepare_model/customize_model_optimizer/Customize_Model_Optimizer.md) guide.
> **NOTE**: This documentation is written based on the [Template extension](https://github.com/openvinotoolkit/openvino/tree/master/docs/template_extension/new), which demonstrates extension development details based on minimalistic `Identity` operation that is a placeholder for your real custom operation. You can review the complete code, which is fully compliable, to see how it works.
## Single Operation Mapping with OpExtension
This section covers the case when a single operation in framework representation is mapped to a single operation in OpenVINO representation. This is called *one-to-one mapping*. There is `OpExtension` class that works well if all the following conditions are satisfied:
1. Number of inputs to operation in the Framework representation is the same as in the OpenVINO representation.
2. Number of outputs is also the same in both representations.
3. Inputs can be indexed and are mapped in order correspondingly, e.g. input with index 0 in framework representation maps to input with index 0 in OpenVINO representation and so on.
4. The same for outputs.
5. Each attribute in OpenVINO operation can be initialized from one of the attributes of original operation or by some predefined constant value. Value of copied attributes cannot contain expressions, value is accepted as-is, so type of a value should be compatible.
> **NOTE**: `OpExtension` class is currently available for ONNX frontend only. PaddlePaddle frontend has named inputs and outputs for operation (not indexed) therefore OpExtension mapping is not applicable for this case.
The next example maps ONNX operation with type [“Identity”]( https://github.com/onnx/onnx/blob/main/docs/Operators.md#Identity) to OpenVINO template extension `Identity` class.
@snippet ov_extensions.cpp frontend_extension_Identity_header
@snippet ov_extensions.cpp frontend_extension_Identity
The mapping doesn’t involve any attributes, as operation Identity doesn’t have them.
Extension objects, like just constructed `extension` can be used to add to the OpenVINO runtime just before the loading a model that contains custom operations:
@snippet ov_extensions.cpp frontend_extension_read_model
Or extensions can be constructed in a separately compiled shared library. Separately compiled library can be used in Model Optimizer or `benchmark_app`. Read about how to build and load such library in chapter “Create library with extensions” in [Introduction to OpenVINO Extension](Intro.md).
If operation have multiple inputs and/or outputs they will be mapped in order. The type of elements in input/output tensors should match expected types in the surrounding operations. For example, if custom operation produces `f32` data type then operation that consumes this output should also support `f32`. Otherwise, model conversion fails with an error, there are no automatic type conversion happens.
### Converting to Standard OpenVINO Operation
`OpExtension` class can be used when mapping to one of the operations from standard OpenVINO operation set is what you need and there is no class like `TemplateExtension::Identity` implemented.
Here is an example for a custom framework operation “MyRelu”. Suppose it is mathematically equivalent to standard `Relu` that exists in OpenVINO operation set, but for some reason has type name “MyRelu”. In this case you can directly say that “MyRelu” -> `Relu` mapping should be used:
@snippet ov_extensions.cpp frontend_extension_MyRelu
In the resulting converted OpenVINO model, “MyRelu” operation will be replaced by the standard operation `Relu` from the latest available OpenVINO operation set. Notice that when standard operation is used, it can be specified using just a type string (“Relu”) instead of using a `ov::opset8::Relu` class name as a template parameter for `OpExtension`. This method is available for operations from the standard operation set only. For a user custom OpenVINO operation the corresponding class should be always specified as a template parameter as it was demonstrated with `TemplateExtension::Identity`.
### Attributes Mapping
As described above, `OpExtension` is useful when attributes can be mapped one by one or initialized by a constant. If the set of attributes in framework representation and OpenVINO representation completely match by their names and types, nothing should be specified in OpExtension constructor parameters. The attributes are discovered and mapped automatically based on `visit_attributes` method that should be defined for any OpenVINO operation.
Imagine you have CustomOperation class implementation that has two attributes with names `attr1` and `attr2`:
@snippet ov_extensions.cpp frontend_extension_CustomOperation
And original model in framework representation also has operation with name “CustomOperatoin” with the same `attr1` and `attr2` attributes. Then with the following code:
@snippet ov_extensions.cpp frontend_extension_CustomOperation_as_is
both `attr1` and `attr2` are copied from framework representation to OpenVINO representation automatically. If for some reason names of attributes are different but values still can be copied “as-is” you can pass attribute names mapping in `OpExtension` constructor:
@snippet ov_extensions.cpp frontend_extension_CustomOperation_rename
Where `fw_attr1` and `fw_attr2` are names for corresponding attributes in framework operation representation.
If copying of an attribute is not what you need, `OpExtension` also can set attribute to predefined constant value. For the same `CustomOperation`, imagine you want to set `attr2` to value 5 instead of copying from `fw_attr2`, to achieve that do the following:
@snippet ov_extensions.cpp frontend_extension_CustomOperation_rename_set
So the conclusion is that each attribute of target OpenVINO operation should be initialized either by
1. Setting automatically due to name matching
2. Mapped by attribute name
3. Set to a constant value
This is achieved by specifying maps as arguments for `OpExtension` constructor.
## Mapping to Multiple Operations with ConversionExtension
Previous sections cover the case when a single operation is mapped to a single operation with optional adjustment in names and attribute values. That is likely enough for your own custom operation with existing C++ kernel implementation. In this case your framework representation and OpenVINO representation for the operation are under your control and inputs/outpus/attributes can be aligned to make `OpExtension` usable.
In case if one-to-one mapping is not possible, *decomposition to multiple operations* should be considered. It is achieved by using more verbose and less automated `ConversionExtension` class. It enables writing arbitrary code to replace a single framework operation by multiple connected OpenVINO operations constructing dependency graph of any complexity.
`ConversionExtension` maps a single operation to a function which builds a graph using OpenVINO operation classes. Follow chapter [Build a Model in OpenVINO Runtime](@ref ov_ug_build_model) to learn how to use OpenVINO operation classes to build a fragment of model for replacement.
The next example illustrates using `ConversionExtension` for conversion of “ThresholdedRelu” from ONNX according to the formula: `ThresholdedRelu(x, alpha) -> Multiply(x, Convert(Greater(x, alpha), type=float))`.
> **NOTE**: `ThresholdedRelu` is one of the standard ONNX operators which is supported by ONNX frontend natively out-of-the-box. Here we are re-implementing it to illustrate how you can add a similar support for your custom operation instead of `ThresholdedRelu`.
@snippet ov_extensions.cpp frontend_extension_ThresholdedReLU_header
@snippet ov_extensions.cpp frontend_extension_ThresholdedReLU
To access original framework operation attribute value and connect to inputs, `node` object of type `NodeContext` is used. It has two main methods:
* `NodeContext::get_input` to get input with a given index,
* `NodeContext::get_attribute` to get attribute value with a given name.
The conversion function should return a vector of node outputs that are mapped to corresponding outputs of the original framework operation in the same order.