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# peerIndex

The unique identifier for a GPU in a peer group.

```
var peerIndex: UInt32 { get }
```

## Discussion

If the GPU is part of a peer group (see [`peerGroupID`](/documentation/Metal/MTLDevice/peerGroupID) or [`peerCount`](/documentation/Metal/MTLDevice/peerCount)) the peer index is the GPU’s unique value within the group in the range `[0, `[`peerCount`](/documentation/Metal/MTLDevice/peerCount)`)`.

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