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# permutation

The tuple that defines the permutation.

```
var permutation: (Int, Int, Int, Int, Int, Int, Int, Int)
```

## 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).

---

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