Remove check for subgraph with cycles

Signed-off-by: Serge Panev <[email protected]>

src/operator/subgraph/build_subgraph.cc

@@ -226,9 +226,7 @@ bool LabelSubgraph(const nnvm::Graph& g, SubgraphSelectorV2Ptr subgraph_selector
     std::stack<const nnvm::Node*> s;
     s.push(descendant);
     size_t count = 0;
-    while (!s.empty()) {
-      CHECK_LT(count, indexed_graph.num_nodes()) << "Finding ancestor failed. There is probably"
-                                                    " a loop in the graph";
+    while (!s.empty() && count < indexed_graph.num_nodes()) {
       ++count;
       const nnvm::Node* top = s.top();
       s.pop();
@@ -276,10 +274,6 @@ bool LabelSubgraph(const nnvm::Graph& g, SubgraphSelectorV2Ptr subgraph_selector
 
   if (excluded_node_id != -1) {
     CHECK_LT(excluded_node_id, static_cast<int>(simple_nodes.size()));
-    CHECK_NE(excluded_node_id, static_cast<int>(snid))
-      << "A cycle is found in the computational graph between nodes "
-      << simple_nodes[excluded_node_id]->node->attrs.name << " and "
-      << simple_nodes[snid]->node->attrs.name;
     excluded_nodes->insert(simple_nodes[excluded_node_id].get());
     ResetNodeLabels(g, simple_nodes, subgraph_nodes);
     return false;