Fix the bug for MEL when adding a recurrent loop.

MachineLearning/cn/ComputationNetwork.h

@@ -1843,6 +1843,13 @@ namespace Microsoft { namespace MSR { namespace CNTK {
 
         void ClearCalcOrderCaches()
         {
+			for (std::map<const ComputationNodePtr, std::list<ComputationNodePtr>>::iterator it = m_cacheEvalOrders.begin(); it != m_cacheEvalOrders.end(); ++it)
+			{
+				for (auto iter2 = m_cacheEvalOrders[it->first].begin(); iter2 != m_cacheEvalOrders[it->first].end(); iter2++)
+				{
+					(*iter2)->clearCache();
+				}
+			}
             m_cacheEvalOrders.clear();
             m_cacheGradientCalcOrders.clear();
         } 
@@ -2043,6 +2050,7 @@ namespace Microsoft { namespace MSR { namespace CNTK {
         void FormRecurentLoops(const ComputationNodePtr rootNode)
         {
             std::vector<ComputationNodePtr> sourceLoopNodes; 
+
             getStrongSCC(rootNode);
             std::list<ComputationNodePtr>&  nodes = GetEvalOrder(rootNode, sourceLoopNodes);
 			std::list<ComputationNodePtr> nodesForGrad;

MachineLearning/cn/ComputationNode.h

@@ -237,6 +237,16 @@ namespace Microsoft { namespace MSR { namespace CNTK {
             m_indexInLoop = index;
         }
 
+		void clearCache()
+		{
+			m_loopId = -1;
+			m_visitedOrder = -1;
+			m_index = -1;
+			m_lowlink = -1;
+			m_indexInLoop = 0;
+			m_visited = false;
+			m_inStack = false;
+		}
         size_t GetIndex()
         {
             return m_index;