onnxruntime/docs/python/api_summary.rst

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2018-11-20 00:48:22 +00:00
===========
API Summary
===========
Summary of public functions and classes exposed
in *ONNX Runtime*.
.. contents::
:local:
IOBinding
=========
By default, *ONNX Runtime* always places input(s) and output(s) on CPU, which
is not optimal if the input or output is consumed and produced on a device
other than CPU because it introduces data copy between CPU and the device.
*ONNX Runtime* provides a feature, *IO Binding*, which addresses this issue by
enabling users to specify which device to place input(s) and output(s) on.
Here are scenarios to use this feature.
(In the following code snippets, *model.onnx* is the model to execute,
*X* is the input data to feed, and *Y* is the output data.)
Scenario 1:
A graph is executed on a deivce other than CPU, for instance CUDA. Users can
use IOBinding to put input on CUDA as the follows.
.. code-block:: python
#X is numpy array on cpu
session = onnxruntime.InferenceSession('model.onnx')
io_binding = session.io_binding()
io_binding.bind_cpu_input('input', X)
io_binding.bind_output('output')
session.run_with_iobinding(io_binding)
Y = io_binding.copy_outputs_to_cpu()[0]
Scenario 2:
The input data is on a device, users direclty use the input. The output data is on CPU.
.. code-block:: python
session = onnxruntime.InferenceSession('model.onnx')
io_binding = session.io_binding()
io_binding.bind_input(name='input', device_type=X.device.type, device_id=0, element_type=np.float32, shape=list(X.size()), buffer_ptr=X.data_ptr())
io_binding.bind_output('output')
session.run_with_iobinding(io_binding)
Y = io_binding.copy_outputs_to_cpu()[0]
Scenario 3:
The input data on a dveice, users directly use the input and also place output on the device:
.. code-block:: python
session = onnxruntime.InferenceSession('model.onnx')
io_binding = session.io_binding()
io_binding.bind_input(name='input', device_type=X.device.type, device_id=0, element_type=np.float32, shape=list(X.size()), buffer_ptr=X.data_ptr())
io_binding.bind_output(name='output', device_type=Y.device.type, device_id=0, element_type=np.float32, shape=list(Y.size()), buffer_ptr=Y.data_ptr())
session.run_with_iobinding(io_binding)
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Device
======
The package is compiled for a specific device, GPU or CPU.
The CPU implementation includes optimizations
such as MKL (Math Kernel Libary). The following function
indicates the chosen option:
.. autofunction:: onnxruntime.get_device
Examples and datasets
=====================
The package contains a few models stored in ONNX format
used in the documentation. These don't need to be downloaded
as they are installed with the package.
.. autofunction:: onnxruntime.datasets.get_example
Load and run a model
====================
*ONNX Runtime* reads a model saved in ONNX format.
The main class *InferenceSession* wraps these functionalities
in a single place.
.. autoclass:: onnxruntime.ModelMetadata
:members:
.. autoclass:: onnxruntime.InferenceSession
:members:
.. autoclass:: onnxruntime.NodeArg
:members:
.. autoclass:: onnxruntime.RunOptions
:members:
.. autoclass:: onnxruntime.SessionOptions
:members:
Backend
=======
In addition to the regular API which is optimized for performance and usability, 
*ONNX Runtime* also implements the
`ONNX backend API <https://github.com/onnx/onnx/blob/master/docs/ImplementingAnOnnxBackend.md>`_
for verification of *ONNX* specification conformance.
The following functions are supported:
.. autofunction:: onnxruntime.backend.is_compatible
.. autofunction:: onnxruntime.backend.prepare
.. autofunction:: onnxruntime.backend.run
.. autofunction:: onnxruntime.backend.supports_device