.. index:: pair: struct; dnnl::lstm_backward::desc
.. _doxid-structdnnl_1_1lstm__backward_1_1desc:

struct dnnl::lstm_backward::desc
================================

.. toctree::
	:hidden:

Overview
~~~~~~~~

Descriptor for an LSTM backward propagation primitive. :ref:`More...<details-structdnnl_1_1lstm__backward_1_1desc>`


.. ref-code-block:: cpp
	:class: doxyrest-overview-code-block

	#include <dnnl.hpp>
	
	struct desc
	{
		// fields
	
		:ref:`dnnl_rnn_desc_t<doxid-structdnnl__rnn__desc__t>` :target:`data<doxid-structdnnl_1_1lstm__backward_1_1desc_1a4d581e6d00f468271ba21f1de20a3ea0>`;

		// construction
	
		:ref:`desc<doxid-structdnnl_1_1lstm__backward_1_1desc_1a39e5609147948d5aedcbe6289420ee3c>`(
			:ref:`prop_kind<doxid-group__dnnl__api__attributes_1gac7db48f6583aa9903e54c2a39d65438f>` aprop_kind,
			:ref:`rnn_direction<doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` direction,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_peephole_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_projection_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& bias_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_peephole_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_projection_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_bias_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_c_desc,
			:ref:`rnn_flags<doxid-group__dnnl__api__rnn_1gad27d0db2a86ae3072207769f5c2ddd1e>` flags = :ref:`rnn_flags::undef<doxid-group__dnnl__api__rnn_1ggad27d0db2a86ae3072207769f5c2ddd1eaf31ee5e3824f1f5e5d206bdf3029f22b>`
			);
	
		:ref:`desc<doxid-structdnnl_1_1lstm__backward_1_1desc_1aefb5f997f5ea15eab34f248320f8ff5f>`(
			:ref:`prop_kind<doxid-group__dnnl__api__attributes_1gac7db48f6583aa9903e54c2a39d65438f>` aprop_kind,
			:ref:`rnn_direction<doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` direction,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_peephole_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& bias_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_peephole_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_bias_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_c_desc,
			:ref:`rnn_flags<doxid-group__dnnl__api__rnn_1gad27d0db2a86ae3072207769f5c2ddd1e>` flags = :ref:`rnn_flags::undef<doxid-group__dnnl__api__rnn_1ggad27d0db2a86ae3072207769f5c2ddd1eaf31ee5e3824f1f5e5d206bdf3029f22b>`
			);
	
		:ref:`desc<doxid-structdnnl_1_1lstm__backward_1_1desc_1a8e8a5662ef97f5ef8586e6ff8363a99e>`(
			:ref:`prop_kind<doxid-group__dnnl__api__attributes_1gac7db48f6583aa9903e54c2a39d65438f>` aprop_kind,
			:ref:`rnn_direction<doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` direction,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& bias_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_c_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_bias_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_layer_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_desc,
			const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_c_desc,
			:ref:`rnn_flags<doxid-group__dnnl__api__rnn_1gad27d0db2a86ae3072207769f5c2ddd1e>` flags = :ref:`rnn_flags::undef<doxid-group__dnnl__api__rnn_1ggad27d0db2a86ae3072207769f5c2ddd1eaf31ee5e3824f1f5e5d206bdf3029f22b>`
			);
	};
.. _details-structdnnl_1_1lstm__backward_1_1desc:

Detailed Documentation
~~~~~~~~~~~~~~~~~~~~~~

Descriptor for an LSTM backward propagation primitive.

Construction
------------

.. index:: pair: function; desc
.. _doxid-structdnnl_1_1lstm__backward_1_1desc_1a39e5609147948d5aedcbe6289420ee3c:

.. ref-code-block:: cpp
	:class: doxyrest-title-code-block

	desc(
		:ref:`prop_kind<doxid-group__dnnl__api__attributes_1gac7db48f6583aa9903e54c2a39d65438f>` aprop_kind,
		:ref:`rnn_direction<doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` direction,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_peephole_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_projection_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& bias_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_peephole_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_projection_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_bias_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_c_desc,
		:ref:`rnn_flags<doxid-group__dnnl__api__rnn_1gad27d0db2a86ae3072207769f5c2ddd1e>` flags = :ref:`rnn_flags::undef<doxid-group__dnnl__api__rnn_1ggad27d0db2a86ae3072207769f5c2ddd1eaf31ee5e3824f1f5e5d206bdf3029f22b>`
		)

Constructs an LSTM (with or without peephole and with or without projection) descriptor for backward propagation using ``prop_kind``, ``direction``, and memory descriptors.

The following arguments may point to a zero memory descriptor:

* ``src_iter_desc`` together with ``src_iter_c_desc``, ``diff_src_iter_desc``, and ``diff_src_iter_c_desc``,

* ``weights_peephole_desc`` together with ``diff_weights_peephole_desc``

* ``bias_desc`` together with ``diff_bias_desc``,

* ``dst_iter_desc`` together with ``dst_iter_c_desc``, ``diff_dst_iter_desc``, and ``diff_dst_iter_c_desc``.

This would then indicate that the LSTM backward propagation primitive should not use them and should default to zero values instead.

The ``weights_projection_desc`` together with ``diff_weights_projection_desc`` may point to a zero memory descriptor. This would then indicate that the LSTM doesn't have recurrent projection layer.

.. note:: 

   All memory descriptors can be initialized with :ref:`dnnl::memory::format_tag::any <doxid-structdnnl_1_1memory_1a8e71077ed6a5f7fb7b3e6e1a5a2ecf3fa100b8cad7cf2a56f6df78f171f97a1ec>` value of ``format_tag``.



.. rubric:: Parameters:

.. list-table::
	:widths: 20 80

	*
		- aprop_kind

		- Propagation kind. Must be :ref:`dnnl::prop_kind::backward <doxid-group__dnnl__api__attributes_1ggac7db48f6583aa9903e54c2a39d65438fa195fe59b6f103787a914aead0f3db502>`.

	*
		- direction

		- RNN direction. See :ref:`dnnl::rnn_direction <doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` for more info.

	*
		- src_layer_desc

		- Memory descriptor for the input vector.

	*
		- src_iter_desc

		- Memory descriptor for the input recurrent hidden state vector.

	*
		- src_iter_c_desc

		- Memory descriptor for the input recurrent cell state vector.

	*
		- weights_layer_desc

		- Memory descriptor for the weights applied to the layer input.

	*
		- weights_iter_desc

		- Memory descriptor for the weights applied to the recurrent input.

	*
		- weights_peephole_desc

		- Memory descriptor for the weights applied to the cell states (according to the Peephole LSTM formula).

	*
		- weights_projection_desc

		- Memory descriptor for the weights applied to the hidden states to get the recurrent projection (according to the Projection LSTM formula).

	*
		- bias_desc

		- Bias memory descriptor.

	*
		- dst_layer_desc

		- Memory descriptor for the output vector.

	*
		- dst_iter_desc

		- Memory descriptor for the output recurrent hidden state vector.

	*
		- dst_iter_c_desc

		- Memory descriptor for the output recurrent cell state vector.

	*
		- diff_src_layer_desc

		- Memory descriptor for the diff of input vector.

	*
		- diff_src_iter_desc

		- Memory descriptor for the diff of input recurrent hidden state vector.

	*
		- diff_src_iter_c_desc

		- Memory descriptor for the diff of input recurrent cell state vector.

	*
		- diff_weights_layer_desc

		- Memory descriptor for the diff of weights applied to the layer input.

	*
		- diff_weights_iter_desc

		- Memory descriptor for the diff of weights applied to the recurrent input.

	*
		- diff_weights_peephole_desc

		- Memory descriptor for the diff of weights applied to the cell states (according to the Peephole LSTM formula).

	*
		- diff_weights_projection_desc

		- Memory descriptor for the diff of weights applied to the hidden states to get the recurrent projection (according to the Projection LSTM formula).

	*
		- diff_bias_desc

		- Diff bias memory descriptor.

	*
		- diff_dst_layer_desc

		- Memory descriptor for the diff of output vector.

	*
		- diff_dst_iter_desc

		- Memory descriptor for the diff of output recurrent hidden state vector.

	*
		- diff_dst_iter_c_desc

		- Memory descriptor for the diff of output recurrent cell state vector.

	*
		- flags

		- Unused.

.. index:: pair: function; desc
.. _doxid-structdnnl_1_1lstm__backward_1_1desc_1aefb5f997f5ea15eab34f248320f8ff5f:

.. ref-code-block:: cpp
	:class: doxyrest-title-code-block

	desc(
		:ref:`prop_kind<doxid-group__dnnl__api__attributes_1gac7db48f6583aa9903e54c2a39d65438f>` aprop_kind,
		:ref:`rnn_direction<doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` direction,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_peephole_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& bias_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_peephole_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_bias_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_c_desc,
		:ref:`rnn_flags<doxid-group__dnnl__api__rnn_1gad27d0db2a86ae3072207769f5c2ddd1e>` flags = :ref:`rnn_flags::undef<doxid-group__dnnl__api__rnn_1ggad27d0db2a86ae3072207769f5c2ddd1eaf31ee5e3824f1f5e5d206bdf3029f22b>`
		)

Constructs an LSTM (with or without peephole) descriptor for backward propagation using ``prop_kind``, ``direction``, and memory descriptors.

The following arguments may point to a zero memory descriptor:

* ``src_iter_desc`` together with ``src_iter_c_desc``, ``diff_src_iter_desc``, and ``diff_src_iter_c_desc``,

* ``weights_peephole_desc`` together with ``diff_weights_peephole_desc``

* ``bias_desc`` together with ``diff_bias_desc``,

* ``dst_iter_desc`` together with ``dst_iter_c_desc``, ``diff_dst_iter_desc``, and ``diff_dst_iter_c_desc``.

This would then indicate that the LSTM backward propagation primitive should not use them and should default to zero values instead.

.. note:: 

   All memory descriptors may be initialized with :ref:`dnnl::memory::format_tag::any <doxid-structdnnl_1_1memory_1a8e71077ed6a5f7fb7b3e6e1a5a2ecf3fa100b8cad7cf2a56f6df78f171f97a1ec>` value of ``format_tag``.



.. rubric:: Parameters:

.. list-table::
	:widths: 20 80

	*
		- aprop_kind

		- Propagation kind. Must be :ref:`dnnl::prop_kind::backward <doxid-group__dnnl__api__attributes_1ggac7db48f6583aa9903e54c2a39d65438fa195fe59b6f103787a914aead0f3db502>`.

	*
		- direction

		- RNN direction. See :ref:`dnnl::rnn_direction <doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` for more info.

	*
		- src_layer_desc

		- Memory descriptor for the input vector.

	*
		- src_iter_desc

		- Memory descriptor for the input recurrent hidden state vector.

	*
		- src_iter_c_desc

		- Memory descriptor for the input recurrent cell state vector.

	*
		- weights_layer_desc

		- Memory descriptor for the weights applied to the layer input.

	*
		- weights_iter_desc

		- Memory descriptor for the weights applied to the recurrent input.

	*
		- weights_peephole_desc

		- Memory descriptor for the weights applied to the cell states (according to the Peephole LSTM formula).

	*
		- bias_desc

		- Bias memory descriptor.

	*
		- dst_layer_desc

		- Memory descriptor for the output vector.

	*
		- dst_iter_desc

		- Memory descriptor for the output recurrent hidden state vector.

	*
		- dst_iter_c_desc

		- Memory descriptor for the output recurrent cell state vector.

	*
		- diff_src_layer_desc

		- Memory descriptor for the diff of input vector.

	*
		- diff_src_iter_desc

		- Memory descriptor for the diff of input recurrent hidden state vector.

	*
		- diff_src_iter_c_desc

		- Memory descriptor for the diff of input recurrent cell state vector.

	*
		- diff_weights_layer_desc

		- Memory descriptor for the diff of weights applied to the layer input.

	*
		- diff_weights_iter_desc

		- Memory descriptor for the diff of weights applied to the recurrent input.

	*
		- diff_weights_peephole_desc

		- Memory descriptor for the diff of weights applied to the cell states (according to the Peephole LSTM formula).

	*
		- diff_bias_desc

		- Diff bias memory descriptor.

	*
		- diff_dst_layer_desc

		- Memory descriptor for the diff of output vector.

	*
		- diff_dst_iter_desc

		- Memory descriptor for the diff of output recurrent hidden state vector.

	*
		- diff_dst_iter_c_desc

		- Memory descriptor for the diff of output recurrent cell state vector.

	*
		- flags

		- Unused.

.. index:: pair: function; desc
.. _doxid-structdnnl_1_1lstm__backward_1_1desc_1a8e8a5662ef97f5ef8586e6ff8363a99e:

.. ref-code-block:: cpp
	:class: doxyrest-title-code-block

	desc(
		:ref:`prop_kind<doxid-group__dnnl__api__attributes_1gac7db48f6583aa9903e54c2a39d65438f>` aprop_kind,
		:ref:`rnn_direction<doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` direction,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& src_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& weights_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& bias_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& dst_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_src_iter_c_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_weights_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_bias_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_layer_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_desc,
		const :ref:`memory::desc<doxid-structdnnl_1_1memory_1_1desc>`& diff_dst_iter_c_desc,
		:ref:`rnn_flags<doxid-group__dnnl__api__rnn_1gad27d0db2a86ae3072207769f5c2ddd1e>` flags = :ref:`rnn_flags::undef<doxid-group__dnnl__api__rnn_1ggad27d0db2a86ae3072207769f5c2ddd1eaf31ee5e3824f1f5e5d206bdf3029f22b>`
		)

Constructs an LSTM descriptor for backward propagation using ``prop_kind``, ``direction``, and memory descriptors.

The following arguments may point to a zero memory descriptor:

* ``src_iter_desc`` together with ``src_iter_c_desc``, ``diff_src_iter_desc``, and ``diff_src_iter_c_desc``,

* ``bias_desc`` together with ``diff_bias_desc``,

* ``dst_iter_desc`` together with ``dst_iter_c_desc``, ``diff_dst_iter_desc``, and ``diff_dst_iter_c_desc``.

This would then indicate that the LSTM backward propagation primitive should not use them and should default to zero values instead.

.. note:: 

   All memory descriptors may be initialized with :ref:`dnnl::memory::format_tag::any <doxid-structdnnl_1_1memory_1a8e71077ed6a5f7fb7b3e6e1a5a2ecf3fa100b8cad7cf2a56f6df78f171f97a1ec>` value of ``format_tag``.



.. rubric:: Parameters:

.. list-table::
	:widths: 20 80

	*
		- aprop_kind

		- Propagation kind. Must be :ref:`dnnl::prop_kind::backward <doxid-group__dnnl__api__attributes_1ggac7db48f6583aa9903e54c2a39d65438fa195fe59b6f103787a914aead0f3db502>`.

	*
		- direction

		- RNN direction. See :ref:`dnnl::rnn_direction <doxid-group__dnnl__api__rnn_1ga33315cf335d1cbe26fd6b70d956e23d5>` for more info.

	*
		- src_layer_desc

		- Memory descriptor for the input vector.

	*
		- src_iter_desc

		- Memory descriptor for the input recurrent hidden state vector.

	*
		- src_iter_c_desc

		- Memory descriptor for the input recurrent cell state vector.

	*
		- weights_layer_desc

		- Memory descriptor for the weights applied to the layer input.

	*
		- weights_iter_desc

		- Memory descriptor for the weights applied to the recurrent input.

	*
		- bias_desc

		- Bias memory descriptor.

	*
		- dst_layer_desc

		- Memory descriptor for the output vector.

	*
		- dst_iter_desc

		- Memory descriptor for the output recurrent hidden state vector.

	*
		- dst_iter_c_desc

		- Memory descriptor for the output recurrent cell state vector.

	*
		- diff_src_layer_desc

		- Memory descriptor for the diff of input vector.

	*
		- diff_src_iter_desc

		- Memory descriptor for the diff of input recurrent hidden state vector.

	*
		- diff_src_iter_c_desc

		- Memory descriptor for the diff of input recurrent cell state vector.

	*
		- diff_weights_layer_desc

		- Memory descriptor for the diff of weights applied to the layer input.

	*
		- diff_weights_iter_desc

		- Memory descriptor for the diff of weights applied to the recurrent input.

	*
		- diff_bias_desc

		- Diff bias memory descriptor.

	*
		- diff_dst_layer_desc

		- Memory descriptor for the diff of output vector.

	*
		- diff_dst_iter_desc

		- Memory descriptor for the diff of output recurrent hidden state vector.

	*
		- diff_dst_iter_c_desc

		- Memory descriptor for the diff of output recurrent cell state vector.

	*
		- flags

		- Unused.