fix the bug when we kill a node whose parent node is still alive

source/tensor/XTensor.cpp

@@ -193,7 +193,7 @@ XTensor::~XTensor()
        the connectivity of the graph. To kill memory
        leak, we release the data of the new tensor
        when its parent is deleted (see ClearIncoming). */
-    if(isTmp && outgo.tailNum > 0){
+    if(outgo.tailNum > 0){
         int dims[MAX_TENSOR_DIM_NUM];
         memcpy(dims, dimSize, order * sizeof(int));
         dims[0] = -dims[0];
@@ -285,6 +285,27 @@ void XTensor::ShallowCopy(const XTensor &tensor)
 /* overloading of the equal-sign */
 XTensor& XTensor::operator= (const XTensor& tensor)
 {
+    /* we must make a hard copy of the tensor if it is the input 
+       of another node. */
+    if(outgo.tailNum > 0){
+        int dims[MAX_TENSOR_DIM_NUM];
+        memcpy(dims, dimSize, order * sizeof(int));
+        dims[0] = -dims[0];
+        
+        XTensor * newTensor = new XTensor(order, dims, dataType, denseRatio, devID, mem);
+        newTensor->SetTMP();
+        newTensor->data = data;
+        newTensor->dataHost = dataHost;
+        
+        XLink::Replace(this, newTensor);
+        XLink::ClearOutgoing(this);
+        XLink::ClearIncoming(this);
+        newTensor->ShallowCopy(this);
+
+        data = NULL;
+        dataHost = NULL;
+    }
+
     /* hard copy of the data array */
     int size = unitNum * unitSize;
     if( isInit && !isSparse && !tensor.isSparse &&