define NULLTensor and NULLList

source/tensor/Main.cpp

@@ -81,15 +81,14 @@ void SmallTest()
     a.Set2D(1.0F, 0, 0);
     a.Set2D(2.0F, 1, 1);
 
-    //b = Sum(a, Multiply(a, a));
+    b = Sum(a, Multiply(a, a));
 
-    /* cannot write this !!!!!!!!!!!!! */
+    /* this is prohibited !!!!!!!!!!!!! */
     //XTensor c = a * b + a;
     //XTensor d = a + b + c.Lin(0.5F);
     
     c = a * b + a;
     d = a + b + c.Lin(0.5F);
-    //d = a + b * b;
 
     XLink::CheckNetwork(&d);
     XLink::ShowNetwork(stderr, &d);

source/tensor/XList.cpp

@@ -42,6 +42,8 @@
 /* the nts (NiuTrans.Tensor) namespace */
 namespace nts{
 
+XList NULLList;
+
 /* constructor */
 XList::XList()
 {

source/tensor/XList.h

@@ -96,6 +96,8 @@ public:
 
 };
 
+extern XList NULLList;
+
 } 
 /* end of the nts (NiuTrans.Tensor) namespace */
 

source/tensor/XTensor.cpp

@@ -61,7 +61,7 @@ namespace nts{
 
 int tensorIDGlobal = 0;
 MUTEX_HANDLE tensorMutex;
-XTensor firstTensor;
+XTensor NULLTensor;
 
 /* generate a tensor id */
 int MakeTensorID()

source/tensor/XTensor.h

@@ -334,7 +334,7 @@ public:
 /* we make a unique id for every tensor */
 extern int tensorIDGlobal;
 extern MUTEX_HANDLE tensorMutex;
-extern XTensor firstTensor;
+extern XTensor NULLTensor;
 extern int MakeTensorID();
 
 /************************************************