Squashed 'subtree/rabit/' changes from 28ca7be..d558f6f

d558f6f redefine distributed means
c8efc01 more complicated yarn script

git-subtree-dir: subtree/rabit
git-subtree-split: d558f6f550

include/rabit/engine.h

@@ -145,6 +145,8 @@ class IEngine {
   virtual int GetRank(void) const = 0;
   /*! \brief gets total number of nodes */
   virtual int GetWorldSize(void) const = 0;
+  /*! \brief whether we run in distribted mode */
+  virtual bool IsDistributed(void) const = 0;
   /*! \brief gets the host name of the current node */
   virtual std::string GetHost(void) const = 0;
   /*!

include/rabit/rabit-inl.h

@@ -107,6 +107,10 @@ inline int GetRank(void) {
 inline int GetWorldSize(void) {
   return engine::GetEngine()->GetWorldSize();
 }
+// whether rabit is distributed
+inline bool IsDistributed(void) {
+  return engine::GetEngine()->IsDistributed();
+}
 // get the name of current processor
 inline std::string GetProcessorName(void) {
   return engine::GetEngine()->GetHost();