1 files changed, 49 insertions, 13 deletions

diff --git a/src/layers/generic.h b/src/layers/generic.h
index 9af033df..b423befe 100644
--- a/src/layers/generic.h
+++ b/src/layers/generic.h
@@ -9,18 +9,19 @@
 
 namespace marian {
 namespace mlp {
-/**
- * @brief Activation functions
- */
+/** Activation functions for MLP layers. */
 enum struct act : int { linear, tanh, sigmoid, ReLU, LeakyReLU, PReLU, swish };
 }  // namespace mlp
 }  // namespace marian
 
 namespace marian {
 
-// Each layer consists of LayerBase and IXXXLayer which defines one or more apply()
-// functions for the respective layer type (different layers may require different signatures).
-// This base class contains configuration info for creating parameters and executing apply().
+/**
+ * Base class for a layer.
+ * Each layer consists of LayerBase and IXXXLayer which defines one or more apply()
+ * functions for the respective layer type (different layers may require different signatures).
+ * This base class contains configuration info for creating parameters and executing apply().
+ */
 class LayerBase {
 protected:
   Ptr<ExpressionGraph> graph_;
@@ -40,22 +41,25 @@ public:
   }
 };
 
-// Simplest layer interface: Unary function
+/** Simplest layer interface: Unary function. */
 struct IUnaryLayer {
   virtual ~IUnaryLayer() {}
+  /** Link a node as the input for this layer. */
   virtual Expr apply(Expr) = 0;
+  /** Link a list of nodes as the inputs for this layer. */
   virtual Expr apply(const std::vector<Expr>& es) {
     ABORT_IF(es.size() > 1, "Not implemented");  // simple stub
     return apply(es.front());
   }
 };
 
+/** Shortlist interface for layers. */
 struct IHasShortList {
   virtual void setShortlist(Ptr<data::Shortlist> shortlist) = 0;
   virtual void clear() = 0;
 };
 
-// Embedding from corpus sub-batch to (emb, mask)
+/** Embedding from corpus sub-batch to (emb, mask). */
 struct IEmbeddingLayer {
   virtual std::tuple<Expr /*embeddings*/, Expr /*mask*/> apply(
       Ptr<data::SubBatch> subBatch) const = 0;
@@ -67,8 +71,10 @@ struct IEmbeddingLayer {
   virtual ~IEmbeddingLayer() {}
 };
 
-// base class for Encoder and Decoder classes, which have embeddings and a batch index (=stream
-// index)
+/**
+ * Base class for Encoder and Decoder classes.
+ * Have embeddings and a batch index (=stream index).
+ */
 class EncoderDecoderLayerBase : public LayerBase {
 protected:
   const std::string prefix_;
@@ -98,16 +104,42 @@ private:
   Ptr<IEmbeddingLayer> createULREmbeddingLayer() const;
 
 public:
-  // get embedding layer; lazily create on first call
+  /**
+   * Get all embedding layer(s).
+   * It lazily creates the embedding layer on first call.
+   * This is lazy mostly because the constructors of the consuming objects are not
+   * guaranteed presently to have access to their graph.
+   * @param ulr whether to use ULREmbedding layer. false by default.
+   * @return a shared pointer to the embedding layer
+   */
   Ptr<IEmbeddingLayer> getEmbeddingLayer(bool ulr = false) const;
 };
 
+/**
+ *  The namespace mlp.
+ *  Declare class Dense and all the available functions for creating
+ *  <a href=https://en.wikipedia.org/wiki/Multilayer_perceptron>multilayer perceptron (MLP)</a>
+ *  network.
+ */
 namespace mlp {
 
+/**
+ * Base class for a fully connected layer.
+ * Implement the operations `output = activation(input * weight + bias)`.
+ */
 class Dense : public LayerBase, public IUnaryLayer {
 public:
+  /**
+   * Construct a dense layer in the graph.
+   * @param graph The expression graph.
+   * @param options The options used for this dense layer.
+   */
   Dense(Ptr<ExpressionGraph> graph, Ptr<Options> options) : LayerBase(graph, options) {}
-
+  /**
+   * Apply/Link a vector of dense layers (with the given inputs) to the expression graph.
+   * @param inputs The vector of the input expressions
+   * @return The expression holding the dense layers
+   */
   Expr apply(const std::vector<Expr>& inputs) override {
     ABORT_IF(inputs.empty(), "No inputs");
 
@@ -161,7 +193,11 @@ public:
     }
     // clang-format on
   };
-
+  /**
+   * Apply/Link this dense layer (with the given input) to the expression graph.
+   * @param input The input expression
+   * @return The expression holding the dense layer
+   */
   Expr apply(Expr input) override { return apply(std::vector<Expr>({input})); }
 };