improve the design of search state

source/sample/transformer/T2TPredictor.h

@@ -28,18 +28,41 @@
 namespace transformer
 {
 
-/* state in decoder - it keeps all previously-generated words and their 
-   hidden states */
+/* state for search. It keeps the path (back-pointer), prediction distribution,
+   and etc. */
 class T2TState
 {
+    /* we assume that the prediction is an integer number */
+    int prediction;
+
+    /* probability of the prediction */
+    float prob;
+
+    /* probability of the path */
+    float pathProb;
+
+    /* pointer to the last state */
+    T2TState * last;
+
+    /* pointers to the following states */
+    XList * followings;
+};
+
+/* a bundle of states */
+class T2TStateBundle
+{
+    /* distribution of every prediction (last state of the path) */
+    XTensor probs;
+
+    /* distribution of every path */
+    XTensor pathProbs;
+
     /* layers on the encoder side. We actually use the encoder output instead
        of all hidden layers. */
-    XList * encoderLayers;
+    XList encoderLayers;
 
     /* layers on the decoder side */
-    XList * decoderLayers;
-
-    /* */
+    XList decoderLayers;
 };
 
 /* The predictor reads the current state and then predicts the next. 
@@ -60,10 +83,10 @@ public:
     ~T2TPredictor();
 
     /* read a state */
-    void Read(T2TModel * model, T2TState * current);
+    void Read(T2TModel * model, T2TStateBundle * current);
 
     /* predict the next state */
-    void Predict(T2TState * next);
+    void Predict(T2TStateBundle * next);
 };
 
 }