---
title: "applyBackward(batchSize:input:output:outputGradient:generatingInputGradient:generatingBiasGradient:)"
framework: accelerate
role: symbol
role_heading: Instance Method
path: "accelerate/bnns/poolinglayer/applybackward(batchsize:input:output:outputgradient:generatinginputgradient:generatingbiasgradient:)"
---

# applyBackward(batchSize:input:output:outputGradient:generatingInputGradient:generatingBiasGradient:)

Applies the layer backward to generate input gradients.

## Declaration

```swift
func applyBackward(batchSize: Int, input: BNNSNDArrayDescriptor, output: BNNSNDArrayDescriptor, outputGradient: BNNSNDArrayDescriptor, generatingInputGradient inputGradient: BNNSNDArrayDescriptor, generatingBiasGradient biasGradient: BNNSNDArrayDescriptor? = nil) throws
```

## Parameters

- `batchSize`: The number of input-output pairs.
- `input`: The descriptor of the input.
- `output`: The descriptor of the output.
- `outputGradient`: The descriptor of the output gradient.
- `inputGradient`: The descriptor of the input gradient.
- `biasGradient`: The descriptor of the bias gradient.

## See Also

### Applying a Pooling Layer

- [apply(batchSize:input:output:)](accelerate/bnns/poolinglayer/apply(batchsize:input:output:).md)