Merge with the branch of huchi.

Support reserved property in XTensor to indicate whether the data is reserved for backward.

source/tensor/XTensor.cpp

@@ -93,6 +93,7 @@ XTensor::XTensor()
     isInGlobalMem = false;
     isInit = false;
     isTmp = false;
+    reserved = 0;
 }
 
 /* constructor */
@@ -158,6 +159,8 @@ XTensor::XTensor(const XTensor& reference)
         devID = reference.devID;
         mem = reference.mem;
         data = reference.data;
+        reserved = reference.reserved;
+        const_cast<XTensor&>(reference).reserved = 0;
         signature = reference.signature;
         const_cast<XTensor&>(reference).data = NULL;
     }
@@ -202,6 +205,8 @@ XTensor::XTensor(const XTensor&& reference)
 
     isInit = true;
     isTmp = reference.isTmp;
+    reserved = reference.reserved;
+    const_cast<XTensor&>(reference).reserved = 0;
 }
 
 /* de-constructor */
@@ -218,8 +223,13 @@ XTensor::~XTensor()
 
         XTensor* newTensor = new XTensor(order, dims, dataType, denseRatio, devID, mem);
         newTensor->SetTMPFlag();
-        newTensor->data = data;
-        data = NULL;
+        if (reserved == -1) {
+            newTensor->data = NULL;
+        }
+        else {
+            newTensor->data = data;
+            data = NULL;
+        }
 
         if (enableGrad)
             XLink::Replace(this, newTensor);
@@ -324,6 +334,11 @@ XTensor& XTensor::operator= (const XTensor& tensor)
         
         XTensor* newTensor = new XTensor(order, dims, dataType, denseRatio, devID, mem);
         newTensor->SetTMPFlag();
+        
+        /* release the data if it won't be used in backward */
+        if (reserved == -1) {
+            DestroyData();
+        }
         newTensor->data = data;
         newTensor->dataHost = dataHost;
         newTensor->signature = tensor.signature;
@@ -409,6 +424,11 @@ XTensor& XTensor::operator= (const XTensor&& tensor)
         
         XTensor* newTensor = new XTensor(order, dims, dataType, denseRatio, devID, mem);
         newTensor->SetTMPFlag();
+
+        /* release the data if it won't be used in backward */
+        if (reserved == -1) {
+            DestroyData();
+        }
         newTensor->data = data;
         newTensor->dataHost = dataHost;
         newTensor->signature = tensor.signature;
@@ -436,9 +456,11 @@ XTensor& XTensor::operator= (const XTensor&& tensor)
     const_cast<XTensor&>(tensor).data = NULL;
 
     if (enableGrad) {
-        XLink::Copy(&tensor, this);
+        XLink::Replace(&tensor, this);
     }
 
+    reserved = tensor.reserved;
+    const_cast<XTensor&>(tensor).reserved = 0;
     return *this;
 }
 

source/tensor/XTensor.h

@@ -142,6 +142,9 @@ public:
     /* indicates whether the tensor is created temporarily */
     bool isTmp;
 
+    /* indicates whether the data is reserved for backward. 0: uncertain; 1: reserved; -1: deletable */
+    int reserved;
+
     /* indicates whether the tensor keeps the gradient when used as model parameters */
     bool isGrad;