> For the complete documentation index, see [llms.txt](https://deeplearning4j.konduit.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://deeplearning4j.konduit.ai/model-import/overview-1/layers-core.md).

# Core Layers

### Keras Core Layer Import

Core layers are implemented in the [layers/core](https://github.com/eclipse/deeplearning4j/tree/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core) package of `deeplearning4j-modelimport`.

#### Support Summary

| Keras Layer            | DL4J Equivalent                                             | Supported |
| ---------------------- | ----------------------------------------------------------- | --------- |
| Dense                  | DenseLayer                                                  | Yes       |
| Activation             | ActivationLayer                                             | Yes       |
| Dropout                | DropoutLayer                                                | Yes       |
| Flatten                | CnnToFeedForwardPreProcessor / RnnToFeedForwardPreProcessor | Yes       |
| Reshape                | ReshapePreProcessor                                         | Yes       |
| Merge                  | MergeVertex                                                 | Yes       |
| Permute                | PermutePreProcessor                                         | Yes       |
| RepeatVector           | RepeatVector                                                | Yes       |
| Lambda                 | SameDiffLambda                                              | Yes       |
| ActivityRegularization | —                                                           | No        |
| Masking                | MaskZeroLayer                                               | Yes       |
| SpatialDropout1D       | DropoutLayer (spatial 1D)                                   | Yes       |
| SpatialDropout2D       | DropoutLayer (spatial 2D)                                   | Yes       |
| SpatialDropout3D       | DropoutLayer (spatial 3D)                                   | Yes       |

***

### KerasPermute

[source](https://github.com/eclipse/deeplearning4j/tree/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasPermute.java)

Imports a Permute layer from Keras as a DL4J input preprocessor.

**Constructor**

```java
public KerasPermute(Map<String, Object> layerConfig)
        throws InvalidKerasConfigurationException, UnsupportedKerasConfigurationException
```

**Parameters:**

* `layerConfig` — dictionary containing Keras layer configuration

**isInputPreProcessor**

```java
public boolean isInputPreProcessor()
```

Returns `true`; Permute is implemented as an input preprocessor in DL4J.

**getInputPreprocessor**

```java
public InputPreProcessor getInputPreprocessor(InputType... inputType)
        throws InvalidKerasConfigurationException
```

Returns the DL4J `InputPreProcessor` corresponding to the Permute configuration.

**getOutputType**

```java
public InputType getOutputType(InputType... inputType) throws InvalidKerasConfigurationException
```

Returns the output `InputType` after permutation.

***

### KerasFlatten

[source](https://github.com/eclipse/deeplearning4j/tree/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasFlatten.java)

Imports a Keras Flatten layer as a DL4J `CnnToFeedForwardInputPreProcessor` or `RnnToFeedForwardPreProcessor`, depending on the preceding layer type.

**Constructor**

```java
public KerasFlatten(Map<String, Object> layerConfig)
        throws InvalidKerasConfigurationException, UnsupportedKerasConfigurationException
```

**isInputPreProcessor**

```java
public boolean isInputPreProcessor()
```

Returns `true`; Flatten is implemented as an input preprocessor.

**getInputPreprocessor**

```java
public InputPreProcessor getInputPreprocessor(InputType... inputType)
        throws InvalidKerasConfigurationException
```

Selects the correct DL4J preprocessor based on `inputType`.

**getOutputType**

```java
public InputType getOutputType(InputType... inputType) throws InvalidKerasConfigurationException
```

***

### KerasReshape

[source](https://github.com/eclipse/deeplearning4j/tree/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasReshape.java)

Imports a Keras Reshape layer as a DL4J input preprocessor.

**Constructor**

```java
public KerasReshape(Map<String, Object> layerConfig)
        throws InvalidKerasConfigurationException, UnsupportedKerasConfigurationException
```

**isInputPreProcessor / getInputPreprocessor / getOutputType**

Same pattern as KerasFlatten above.

***

### KerasMerge

[source](https://github.com/eclipse/deeplearning4j/tree/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasMerge.java)

Imports a Keras Merge layer as a DL4J graph vertex. Supports `add`, `multiply`, `subtract`, `average`, `maximum`, and `concatenate` modes. The `dot` mode is not supported.

**Constructor**

```java
public KerasMerge(Integer kerasVersion) throws UnsupportedKerasConfigurationException
```

**getOutputType**

```java
public InputType getOutputType(InputType... inputType)
```

***

### KerasDense

[source](https://github.com/eclipse/deeplearning4j/tree/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasDense.java)

Imports a Keras Dense layer as a DL4J `DenseLayer`.

**Constructor**

```java
public KerasDense(Map<String, Object> layerConfig)
        throws InvalidKerasConfigurationException, UnsupportedKerasConfigurationException
```

**getDenseLayer**

```java
public DenseLayer getDenseLayer()
```

Returns the DL4J `DenseLayer`.

**getOutputType**

```java
public InputType getOutputType(InputType... inputType) throws InvalidKerasConfigurationException
```

**getNumParams**

```java
public int getNumParams()
```

Returns the number of trainable parameters (weights + bias).

**setWeights**

```java
public void setWeights(Map<String, INDArray> weights) throws InvalidKerasConfigurationException
```

***

### KerasDropout

[source](https://github.com/eclipse/deeplearning4j/tree/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasDropout.java)

Imports a Keras Dropout layer as a DL4J `DropoutLayer`.

**Constructor**

```java
public KerasDropout(Map<String, Object> layerConfig)
        throws InvalidKerasConfigurationException, UnsupportedKerasConfigurationException
```

**getDropoutLayer**

```java
public DropoutLayer getDropoutLayer()
```

**getOutputType**

```java
public InputType getOutputType(InputType... inputType) throws InvalidKerasConfigurationException
```

***

### KerasMasking

[source](https://github.com/eclipse/deeplearning4j/blob/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasMasking.java)

Imports a Keras Masking layer as a DL4J `MaskZeroLayer`.

***

### KerasSpatialDropout

[source](https://github.com/eclipse/deeplearning4j/blob/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasSpatialDropout.java)

Imports Keras SpatialDropout1D, SpatialDropout2D, and SpatialDropout3D layers as DL4J spatial dropout variants.

***

### KerasLambda

[source](https://github.com/eclipse/deeplearning4j/blob/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasLambda.java)

Imports a Keras Lambda layer. The Lambda layer is mapped to a SameDiff-based lambda function in DL4J. The function body is serialized separately.

***

### KerasRepeatVector

[source](https://github.com/eclipse/deeplearning4j/blob/master/deeplearning4j/deeplearning4j-modelimport/src/main/java/org/deeplearning4j/nn/modelimport/keras/layers/core/KerasRepeatVector.java)

Imports a Keras RepeatVector layer, which repeats the input a fixed number of times along a new axis.

***

### Notes

* `ActivityRegularization` has no direct DL4J equivalent and will throw `UnsupportedKerasConfigurationException` at import time. Apply regularization directly in the layer configuration instead.
* The Permute, Flatten, and Reshape layers are all implemented as `InputPreProcessor` instances in DL4J rather than as trainable layers.