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# BNNS.DescriptorType

Constants that describe the input and output types of an arithmetic operation.

```
enum DescriptorType
```

## Topics

### Descriptor Types

[`case constant`](/documentation/Accelerate/BNNS/DescriptorType/constant)

A constant that doesn’t have a gradient.

[`case parameter`](/documentation/Accelerate/BNNS/DescriptorType/parameter)

A parameter that’s trainable, such as weights or bias.

[`case sample`](/documentation/Accelerate/BNNS/DescriptorType/sample)

A sample such as input or output.

## Relationships

### Conforms To

[`Equatable`](/documentation/Swift/Equatable)

[`Hashable`](/documentation/Swift/Hashable)

---

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