Add RepeatVector layer (#139)

* Added missing saving functions for ReLU and ELU activation layers (JetBrains#78)

* Reverted changes to the imports

* Added RepeatVector layer #123

* Added serialisation support for RepeatVector layer #123

* Wrote test for RepeatVector #123

* Made changed requested by avan (see desc.)
- added missing require check in init block of RepeatVector
- updated docs
- reformatted code
- housekeeping

* Removed redundant Obs.repeat ext fun

* Made changed requested by avan (see desc.)

- change require message in computeOutputShape
- used inputShape.size(...) for creating shape
- removed author tag

* Used `=` instead of `return` block, added TODO

* Implemented changes requested by zaleslaw

- save trainability status
- renamed tests

* Added test for negative `n` #123

* Added missing newline

api/src/main/kotlin/org/jetbrains/kotlinx/dl/api/core/layer/reshaping/RepeatVector.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2021 JetBrains s.r.o. and Kotlin Deep Learning project contributors. All Rights Reserved.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlinx.dl.api.core.layer.reshaping
+
+import org.jetbrains.kotlinx.dl.api.core.KGraph
+import org.jetbrains.kotlinx.dl.api.core.layer.Layer
+import org.tensorflow.Operand
+import org.tensorflow.Shape
+import org.tensorflow.op.Ops
+
+/**
+ * Layer that repeats the input [n] times.
+ *
+ * Input shape: `2D tensor of shape (num_samples, features)`.
+ *
+ * Output shape: `3D tensor of shape (num_samples, n, features)`.
+ *
+ * @property n Repetition factor.
+ * @property [name] Custom layer name.
+ * @constructor Creates [RepeatVector] object.
+ *
+ * @since 0.3
+ */
+public class RepeatVector(
+    public val n: Int,
+    name: String = ""
+) : Layer(name) {
+
+    init {
+        require(n >= 1) { "Number of repetitions (n) in RepeatVector should be positive but got $n" }
+    }
+
+    override fun build(tf: Ops, kGraph: KGraph, inputShape: Shape): Unit = Unit
+
+    override fun computeOutputShape(inputShape: Shape): Shape {
+        require(inputShape.numDimensions() == 2) {
+            "Input tensor must have 2 dimensions but got ${inputShape.numDimensions()}"
+        }
+        return Shape.make(inputShape.size(0), n.toLong(), inputShape.size(1))
+    }
+
+    override fun forward(
+        tf: Ops,
+        input: Operand<Float>,
+        isTraining: Operand<Boolean>,
+        numberOfLosses: Operand<Float>?
+    ): Operand<Float> {
+        val x = tf.expandDims(input, tf.constant(1))
+        val pattern = tf.stack(listOf(tf.constant(1), tf.constant(n), tf.constant(1)))
+        return tf.tile(x, pattern)
+    }
+
+    override var weights: Map<String, Array<*>>
+        get() = emptyMap()
+        set(value) = assignWeights(value)
+
+    override val hasActivation: Boolean get() = false
+
+    override val paramCount: Int get() = 0
+
+    override fun toString(): String {
+        return "RepeatVector"
+    }
+}

api/src/main/kotlin/org/jetbrains/kotlinx/dl/api/inference/keras/KerasConstants.kt

@@ -38,6 +38,7 @@ internal const val LAYER_DROPOUT: String = "Dropout"
 // Attention layers
 // Reshaping layers
 internal const val LAYER_FLATTEN: String = "Flatten"
+internal const val LAYER_REPEAT_VECTOR: String = "RepeatVector"
 internal const val LAYER_RESHAPE: String = "Reshape"
 internal const val LAYER_ZERO_PADDING_2D = "ZeroPadding2D"
 internal const val LAYER_CROPPING_2D = "Cropping2D"

api/src/main/kotlin/org/jetbrains/kotlinx/dl/api/inference/keras/ModelLoader.kt

@@ -22,6 +22,7 @@ import org.jetbrains.kotlinx.dl.api.core.layer.pooling.*
 import org.jetbrains.kotlinx.dl.api.core.layer.regularization.Dropout
 import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.Cropping2D
 import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.Flatten
+import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.RepeatVector
 import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.Reshape
 import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.ZeroPadding2D
 import org.jetbrains.kotlinx.dl.api.core.regularizer.L1
@@ -142,6 +143,7 @@ private fun convertToLayer(
         // Attention layers
         // Reshaping layers
         LAYER_FLATTEN -> createFlattenLayer(kerasLayer.config!!.name!!)
+        LAYER_REPEAT_VECTOR -> createRepeatVectorLayer(kerasLayer.config!!, kerasLayer.config.name!!)
         LAYER_RESHAPE -> createReshapeLayer(kerasLayer.config!!, kerasLayer.config.name!!)
         LAYER_CROPPING_2D -> createCropping2DLayer(kerasLayer.config!!, kerasLayer.config.name!!)
         LAYER_ZERO_PADDING_2D -> createZeroPadding2DLayer(kerasLayer.config!!, kerasLayer.config.name!!)
@@ -722,6 +724,10 @@ private fun createFlattenLayer(name: String): Layer {
     return Flatten(name = name)
 }
 
+private fun createRepeatVectorLayer(config: LayerConfig, name: String): Layer {
+    return RepeatVector(name = name, n = config.n!!)
+}
+
 private fun createReshapeLayer(config: LayerConfig, name: String): Layer {
     return Reshape(name = name, targetShape = config.target_shape!!)
 }

api/src/main/kotlin/org/jetbrains/kotlinx/dl/api/inference/keras/ModelSaver.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlinx.dl.api.core.layer.merge.*
 import org.jetbrains.kotlinx.dl.api.core.layer.normalization.BatchNorm
 import org.jetbrains.kotlinx.dl.api.core.layer.pooling.*
 import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.Flatten
+import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.RepeatVector
 import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.ZeroPadding2D
 import org.jetbrains.kotlinx.dl.api.core.regularizer.L2L1
 import org.jetbrains.kotlinx.dl.api.core.regularizer.Regularizer
@@ -98,6 +99,7 @@ private fun convertToKerasLayer(layer: Layer, isKerasFullyCompatible: Boolean, i
         // Attention layers
         // Reshaping layers
         is Flatten -> createKerasFlattenLayer(layer)
+        is RepeatVector -> createKerasRepeatVectorLayer(layer)
         is ZeroPadding2D -> createKerasZeroPadding2DLayer(layer)
         // Merging layers
         is Add -> createKerasAddLayer(layer)
@@ -584,6 +586,17 @@ private fun createKerasFlattenLayer(layer: Flatten): KerasLayer {
     return KerasLayer(class_name = LAYER_FLATTEN, config = configX)
 }
 
+private fun createKerasRepeatVectorLayer(layer: RepeatVector): KerasLayer {
+    val configX = LayerConfig(
+        data_format = CHANNELS_LAST,
+        dtype = DATATYPE_FLOAT32,
+        trainable = layer.isTrainable,
+        name = layer.name,
+        n = layer.n
+    )
+    return KerasLayer(class_name = LAYER_REPEAT_VECTOR, config = configX)
+}
+
 private fun createKerasConcatenateLayer(layer: Concatenate): KerasLayer {
     val configX = LayerConfig(
         dtype = DATATYPE_FLOAT32,

api/src/main/kotlin/org/jetbrains/kotlinx/dl/api/inference/keras/config/LayerConfig.kt

@@ -85,6 +85,8 @@ internal data class LayerConfig(
     @Json(serializeNull = false)
     val moving_variance_initializer: KerasInitializer? = null,
     @Json(serializeNull = false)
+    val n: Int? = null,
+    @Json(serializeNull = false)
     val name: String? = null,
     @Json(serializeNull = false)
     val negative_slope: Double? = null,

api/src/test/kotlin/org/jetbrains/kotlinx/dl/api/core/layer/RepeatVectorLayerTest.kt

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2021 JetBrains s.r.o. and Kotlin Deep Learning project contributors. All Rights Reserved.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlinx.dl.api.core.layer
+
+import org.jetbrains.kotlinx.dl.api.core.KGraph
+import org.jetbrains.kotlinx.dl.api.core.layer.reshaping.RepeatVector
+import org.jetbrains.kotlinx.dl.api.core.shape.toIntArray
+import org.junit.jupiter.api.Assertions
+import org.junit.jupiter.api.Test
+import org.tensorflow.Graph
+import org.tensorflow.Output
+import org.tensorflow.Shape
+import org.tensorflow.op.Ops
+
+internal class RepeatVectorLayerTest {
+
+    @Test
+    fun testIllegalRepetitions() {
+        Assertions.assertThrows(IllegalArgumentException::class.java) {
+            RepeatVector(n = -10)
+        }
+    }
+
+    @Test
+    fun testOutputShape() {
+        val layer = RepeatVector(n = 2)
+        val x = Array(10) { FloatArray(10) { 1F } }
+        val y = layer(x)
+        Assertions.assertArrayEquals(intArrayOf(10, layer.n, 10), y.shape().toIntArray())
+    }
+
+    @Test
+    fun testOutput() {
+        val layer = RepeatVector(n = 2)
+        val x = Array(3) { FloatArray(3) { it.toFloat() } }
+        val y = layer(x)
+        val actual = y.tensor().copyTo(Array(3) { Array(layer.n) { FloatArray(3) } })
+        val expected = arrayOf(
+            arrayOf(floatArrayOf(0F, 1F, 2F), floatArrayOf(0F, 1F, 2F)),
+            arrayOf(floatArrayOf(0F, 1F, 2F), floatArrayOf(0F, 1F, 2F)),
+            arrayOf(floatArrayOf(0F, 1F, 2F), floatArrayOf(0F, 1F, 2F))
+        )
+        Assertions.assertArrayEquals(expected, actual)
+    }
+
+    // TODO: generalise this for Layer, see https://github.com/JetBrains/KotlinDL/issues/145
+    private operator fun RepeatVector.invoke(input: Array<FloatArray>): Output<Float> = Ops.create().let { tf ->
+        build(tf, KGraph(Graph().toGraphDef()), Shape.make(10, 10))
+        val inputOp = tf.constant(input)
+        val isTraining = tf.constant(true)
+        val numberOfLosses = tf.constant(1.0f)
+        forward(tf, inputOp, isTraining, numberOfLosses).asOutput()
+    }
+}