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# init(i_desc:o_desc:permutation:)

Returns a new permute layer parameters structure from the specified parameters.

```
init(i_desc: BNNSNDArrayDescriptor, o_desc: BNNSNDArrayDescriptor, permutation: (Int, Int, Int, Int, Int, Int, Int, Int))
```

## Parameters

`i_desc`

The descriptor of the input.

`o_desc`

The descriptor of the output.

`permutation`

The tuple that defines the permutation.

## Discussion

Use the permutation array to specify the input axis source for the corresponding output axis source. For example, a permutation array [2,1,0] applied on a [`BNNSDataLayoutImageCHW`](/documentation/Accelerate/BNNSDataLayoutImageCHW) tensor results in axis reverse (that is, output axis 0 is input axis 2, output axis 1 is input axis 1, and output axis 2 is input axis 0).

> Important:
> The number of input dimensions must be equal to number of output dimensions.

---

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