---
title: output_descriptor
framework: accelerate
role: symbol
role_heading: Instance Property
path: accelerate/bnnslayerparameterslstm/output_descriptor
---

# output_descriptor

Descriptors of the output, hidden output, and cell-state output data.

## Declaration

```swift
var output_descriptor: BNNSLSTMDataDescriptor
```

## Discussion

Discussion You must define the layout of this descriptor as one of either: BNNSDataLayoutSNE with the shape (num_directions*hidden_size,batch_size,seq_len) BNNSDataLayoutNSE with the shape (num_directions*hidden_size,seq_len,batch_size) BNNS can upack the first dimension as a 2D array with hidden_size as the major dimension. That is, BNNS can interpret the dimension as a C array with the shape [num_directions][ hidden_size ]. If lstm_flags includes BNNSLayerFlagsLSTMBidirectional, BNNS defines num_directions as 2, or otherwise 1. If you don’t specify a layout, BNNS uses BNNSDataLayoutSNE. Use C style multidimensional array notation to define the hierarchy of the hidden_desc and cell_state_desc descriptors as [num_layers][num_directions][batch_size][hidden_size].

## See Also

### Instance Properties

- [input_size](accelerate/bnnslayerparameterslstm/input_size.md)
- [hidden_size](accelerate/bnnslayerparameterslstm/hidden_size.md)
- [batch_size](accelerate/bnnslayerparameterslstm/batch_size.md)
- [num_layers](accelerate/bnnslayerparameterslstm/num_layers.md)
- [seq_len](accelerate/bnnslayerparameterslstm/seq_len.md)
- [dropout](accelerate/bnnslayerparameterslstm/dropout.md)
- [lstm_flags](accelerate/bnnslayerparameterslstm/lstm_flags.md)
- [sequence_descriptor](accelerate/bnnslayerparameterslstm/sequence_descriptor.md)
- [input_descriptor](accelerate/bnnslayerparameterslstm/input_descriptor.md)
- [input_gate](accelerate/bnnslayerparameterslstm/input_gate.md)
- [forget_gate](accelerate/bnnslayerparameterslstm/forget_gate.md)
- [candidate_gate](accelerate/bnnslayerparameterslstm/candidate_gate.md)
- [output_gate](accelerate/bnnslayerparameterslstm/output_gate.md)
- [hidden_activation](accelerate/bnnslayerparameterslstm/hidden_activation.md)