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  "identifier" : "/documentation/Accelerate/BNNS/LossLayer/init(input:output:lossFunction:lossReduction:filterParameters:)",
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# init(input:output:lossFunction:lossReduction:filterParameters:)

Returns a new loss layer.

```
convenience init?(input: BNNSNDArrayDescriptor, output: BNNSNDArrayDescriptor, lossFunction: BNNS.LossFunction, lossReduction: BNNS.LossReduction, filterParameters: BNNSFilterParameters? = nil)
```

## Parameters

`input`

The descriptor of the input.

`output`

The descriptor of the output.

`lossFunction`

The function that’s used to compute the loss.

`lossReduction`

The function that’s used to reduce the computed loss.

`filterParameters`

The filter runtime parameters.

## Discussion

> Important:
> The input data type and output data type must be `float`. The output size must be `1`, unless the reduction is ``doc://com.apple.accelerate/documentation/Accelerate/BNNS/LossReduction/none``.

---

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