Bug fixed.

Fix the memory pool bug in SetDevice function.

source/tensor/XTensor.cpp

@@ -520,13 +520,11 @@ relocate the data on the target device
 */
 void XTensor::SetDevice(int myDevId, XMem * myMem)
 {
-    if (myMem != NULL) {
-        FlushToMem(myMem);
-        isInGlobalMem = false;
-    }
-    else {
+    if (myMem == NULL) {
         myMem = GMems.GetMem(myDevId);
     }
+    FlushToMem(myMem);
+    isInGlobalMem = false;
 }
 
 bool XTensor::IsReduceShaped(const XTensor * a, const XTensor * b, int dim)