[GraphBuilder] Use last added layer/vertex if no inputs specified

deeplearning4j/deeplearning4j-core/src/test/java/org/deeplearning4j/nn/conf/ComputationGraphConfigurationTest.java

@@ -54,9 +54,8 @@ public void testJSONBasic() {
                 .optimizationAlgo(OptimizationAlgorithm.STOCHASTIC_GRADIENT_DESCENT)
                 .dist(new NormalDistribution(0, 1)).updater(new NoOp())
                 .graphBuilder().addInputs("input")
-                .addLayer("firstLayer",
-                        new DenseLayer.Builder().nIn(4).nOut(5).activation(Activation.TANH).build(),
-                        "input")
+                .appendLayer("firstLayer",
+                        new DenseLayer.Builder().nIn(4).nOut(5).activation(Activation.TANH).build())
                 .addLayer("outputLayer",
                         new OutputLayer.Builder().lossFunction(LossFunctions.LossFunction.MCXENT)
                                 .activation(Activation.SOFTMAX).nIn(5).nOut(3).build(),
@@ -153,6 +152,18 @@ public void testInvalidConfigurations() {
             //e.printStackTrace();
         }
 
+        // Use appendLayer on first layer
+        try {
+            new NeuralNetConfiguration.Builder().graphBuilder()
+                    .appendLayer("dense1", new DenseLayer.Builder().nIn(2).nOut(2).build())
+                    .addLayer("out", new OutputLayer.Builder().nIn(2).nOut(2).build()).setOutputs("out")
+                    .build();
+            fail("No exception thrown for invalid configuration");
+        } catch (IllegalStateException e) {
+            //OK - exception is good
+            //e.printStackTrace();
+        }
+
         //Test no network inputs
         try {
             new NeuralNetConfiguration.Builder().graphBuilder()

deeplearning4j/deeplearning4j-nn/src/main/java/org/deeplearning4j/nn/conf/ComputationGraphConfiguration.java

@@ -662,6 +662,8 @@ public static class GraphBuilder {
         protected boolean validateOutputConfig = true;
         protected boolean validateTbpttConfig = true;
 
+        protected String lastAdded = null;
+
         public GraphBuilder(NeuralNetConfiguration.Builder globalConfiguration) {
             this.globalConfiguration = globalConfiguration;
         }
@@ -754,20 +756,32 @@ public GraphBuilder tBPTTLength(int tbpttLength){
          *
          * @param layerName   Name/label of the layer to add
          * @param layer       The layer configuration
-         * @param layerInputs Inputs to this layer (must be 1 or more). Inputs may be other layers, GraphVertex objects,
+         * @param layerInputs Inputs to this layer. Inputs may be other layers, GraphVertex objects,
          *                    on a combination of the two.
          * @see #addLayer(String, Layer, InputPreProcessor, String...)
          */
         public GraphBuilder addLayer(String layerName, Layer layer, String... layerInputs) {
             return addLayer(layerName, layer, null, layerInputs);
         }
 
+        /**
+         * Add a layer, with no {@link InputPreProcessor}, with the specified name
+         * and input from the last added layer/vertex.
+         *
+         * @param layerName   Name/label of the layer to add
+         * @param layer       The layer configuration
+         * @see #addLayer(String, Layer, InputPreProcessor, String...)
+         */
+        public GraphBuilder appendLayer(String layerName, Layer layer) {
+            return appendLayer(layerName, layer, null);
+        }
+
         /**
          * Add a layer, with no {@link InputPreProcessor}, with the specified name and specified inputs.
          *
          * @param layerName   Name/label of the layer to add
          * @param layer       The layer configuration
-         * @param layerInputs Inputs to this layer (must be 1 or more). Inputs may be other layers, GraphVertex objects,
+         * @param layerInputs Inputs to this layer. Inputs may be other layers, GraphVertex objects,
          *                    on a combination of the two.
          * @see #addLayer(String, Layer, InputPreProcessor, String...)
          */
@@ -780,7 +794,7 @@ public GraphBuilder layer(int layerName, Layer layer, String... layerInputs) {
          *
          * @param layerName   Name/label of the layer to add
          * @param layer       The layer configuration
-         * @param layerInputs Inputs to this layer (must be 1 or more). Inputs may be other layers, GraphVertex objects,
+         * @param layerInputs Inputs to this layer. Inputs may be other layers, GraphVertex objects,
          *                    on a combination of the two.
          * @see #addLayer(String, Layer, InputPreProcessor, String...)
          */
@@ -794,7 +808,7 @@ public GraphBuilder layer(String layerName, Layer layer, String... layerInputs)
          * @param layerName    Name/label of the layer to add
          * @param layer        The layer configuration
          * @param preProcessor The InputPreProcessor to use with this layer.
-         * @param layerInputs  Inputs to this layer (must be 1 or more). Inputs may be other layers, GraphVertex objects,
+         * @param layerInputs  Inputs to this layer. Inputs may be other layers, GraphVertex objects,
          *                     on a combination of the two.
          */
         public GraphBuilder addLayer(String layerName, Layer layer, InputPreProcessor preProcessor,
@@ -806,13 +820,31 @@ public GraphBuilder addLayer(String layerName, Layer layer, InputPreProcessor pr
             return this;
         }
 
+        /**
+         * Add a layer and an {@link InputPreProcessor}, with the specified name
+         * and input from the last added layer/vertex.
+         *
+         * @param layerName    Name/label of the layer to add
+         * @param layer        The layer configuration
+         * @param preProcessor The InputPreProcessor to use with this layer.
+         */
+        public GraphBuilder appendLayer(String layerName, Layer layer, InputPreProcessor preProcessor) {
+
+            if(lastAdded == null){
+                throw new IllegalStateException("Can not use appendLayer with no previous layers");
+            }
+
+            addLayer(layerName, layer, preProcessor, lastAdded);
+            return this;
+        }
+
         /**
          * Add a layer and an {@link InputPreProcessor}, with the specified name and specified inputs.
          *
          * @param layerName    Name/label of the layer to add
          * @param layer        The layer configuration
          * @param preProcessor The InputPreProcessor to use with this layer.
-         * @param layerInputs  Inputs to this layer (must be 1 or more). Inputs may be other layers, GraphVertex objects,
+         * @param layerInputs  Inputs to this layer. Inputs may be other layers, GraphVertex objects,
          *                     on a combination of the two.
          */
         public GraphBuilder layer(String layerName, Layer layer, InputPreProcessor preProcessor,
@@ -881,6 +913,7 @@ public GraphBuilder removeVertex(String vertexName, boolean removeConnections) {
          */
         public GraphBuilder addInputs(String... inputNames) {
             Collections.addAll(networkInputs, inputNames);
+            lastAdded = networkInputs.get(networkInputs.size() - 1);
             return this;
         }
 
@@ -891,6 +924,7 @@ public GraphBuilder addInputs(String... inputNames) {
          */
         public GraphBuilder addInputs(Collection<String> inputNames) {
             networkInputs.addAll(inputNames);
+            lastAdded = networkInputs.get(networkInputs.size() - 1);
             return this;
         }
 
@@ -934,9 +968,10 @@ public GraphBuilder setOutputs(String... outputNames) {
          *
          * @param vertexName   The name of the GraphVertex to add
          * @param vertex       The GraphVertex to add
-         * @param vertexInputs The inputs/activations to this GraphVertex
+         * @param vertexInputs The inputs/activations to this GraphVertex.
          */
         public GraphBuilder addVertex(String vertexName, GraphVertex vertex, String... vertexInputs) {
+
             Preconditions.checkState(!vertices.containsKey(vertexName), "Cannot add vertex: a vertex with name \"%s\" already exists", vertexName);
             vertices.put(vertexName, vertex);
 
@@ -948,6 +983,29 @@ public GraphBuilder addVertex(String vertexName, GraphVertex vertex, String... v
             } else if (vertexInputs != null) {
                 this.vertexInputs.put(vertexName, Arrays.asList(vertexInputs));
             }
+
+            this.lastAdded = vertexName;
+
+            return this;
+        }
+
+        /**
+         * Add a {@link GraphVertex} to the network configuration, with input from the last added vertex/layer. A GraphVertex defines forward and backward pass methods,
+         * and can contain a {@link LayerVertex}, a {@link org.deeplearning4j.nn.conf.graph.ElementWiseVertex} to do element-wise
+         * addition/subtraction, a {@link MergeVertex} to combine/concatenate the activations out of multiple layers or vertices,
+         * a {@link org.deeplearning4j.nn.conf.graph.SubsetVertex} to select a subset of the activations out of another layer/GraphVertex.<br>
+         * Custom GraphVertex objects (that extend the abstract {@link GraphVertex} class) may also be used.
+         *
+         * @param vertexName   The name of the GraphVertex to add
+         * @param vertex       The GraphVertex to add
+         */
+        public GraphBuilder appendVertex(String vertexName, GraphVertex vertex) {
+
+            if(lastAdded == null){
+                throw new IllegalStateException("Can not use appendLayer with no previous layers");
+            }
+
+            addVertex(vertexName, vertex, lastAdded);
             return this;
         }