diff --git a/subtree/rabit/include/rabit.h b/subtree/rabit/include/rabit.h
index eb2834b30..7e3b88cdf 100644
--- a/subtree/rabit/include/rabit.h
+++ b/subtree/rabit/include/rabit.h
@@ -65,9 +65,8 @@ inline int GetRank(void);
 /*! \brief gets total number of processes */
 inline int GetWorldSize(void);
 /*! \brief whether rabit env is in distributed mode */
-inline bool IsDistributed(void) {
-  return GetWorldSize() != 1;
-}
+inline bool IsDistributed(void);
+
 /*! \brief gets processor's name */
 inline std::string GetProcessorName(void);
 /*!
diff --git a/subtree/rabit/include/rabit/engine.h b/subtree/rabit/include/rabit/engine.h
index 668b4fcef..e0395cdcd 100644
--- a/subtree/rabit/include/rabit/engine.h
+++ b/subtree/rabit/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;
   /*!
diff --git a/subtree/rabit/include/rabit/rabit-inl.h b/subtree/rabit/include/rabit/rabit-inl.h
index e0a14f4ad..21d15d9e1 100644
--- a/subtree/rabit/include/rabit/rabit-inl.h
+++ b/subtree/rabit/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();
diff --git a/subtree/rabit/src/allreduce_base.h b/subtree/rabit/src/allreduce_base.h
index 00dc60754..41b9f35f2 100644
--- a/subtree/rabit/src/allreduce_base.h
+++ b/subtree/rabit/src/allreduce_base.h
@@ -63,6 +63,10 @@ class AllreduceBase : public IEngine {
     if (world_size == -1) return 1;
     return world_size;
   }
+  /*! \brief whether is distributed or not */
+  virtual bool IsDistributed(void) const {
+    return tracker_uri == "NULL";
+  }
   /*! \brief get rank */
   virtual std::string GetHost(void) const {
     return host_uri;
diff --git a/subtree/rabit/src/engine_empty.cc b/subtree/rabit/src/engine_empty.cc
index a29a35b0c..35e2a07d1 100644
--- a/subtree/rabit/src/engine_empty.cc
+++ b/subtree/rabit/src/engine_empty.cc
@@ -56,6 +56,10 @@ class EmptyEngine : public IEngine {
   virtual int GetWorldSize(void) const {
     return 1;
   }
+  /*! \brief whether it is distributed */
+  virtual bool IsDistributed(void) const {
+    return false;
+  }
   /*! \brief get the host name of current node */
   virtual std::string GetHost(void) const {
     return std::string("");
diff --git a/subtree/rabit/src/engine_mpi.cc b/subtree/rabit/src/engine_mpi.cc
index 829051231..c434e71d0 100644
--- a/subtree/rabit/src/engine_mpi.cc
+++ b/subtree/rabit/src/engine_mpi.cc
@@ -59,6 +59,10 @@ class MPIEngine : public IEngine {
   virtual int GetWorldSize(void) const {
     return MPI::COMM_WORLD.Get_size();
   }
+  /*! \brief whether it is distributed */
+  virtual bool IsDistributed(void) const {
+    return true;
+  }
   /*! \brief get the host name of current node */
   virtual std::string GetHost(void) const {
     int len;
diff --git a/subtree/rabit/tracker/rabit_yarn.py b/subtree/rabit/tracker/rabit_yarn.py
index 04074e618..81f590851 100755
--- a/subtree/rabit/tracker/rabit_yarn.py
+++ b/subtree/rabit/tracker/rabit_yarn.py
@@ -16,7 +16,7 @@ YARN_JAR_PATH = os.path.dirname(__file__) + '/../yarn/rabit-yarn.jar'
 
 if not os.path.exists(YARN_JAR_PATH):
     warnings.warn("cannot find \"%s\", I will try to run build" % YARN_JAR_PATH)
-    cmd = 'cd %;./build.sh' % os.path.dirname(__file__) + '/../yarn/'
+    cmd = 'cd %s;./build.sh' % (os.path.dirname(__file__) + '/../yarn/')
     print cmd
     subprocess.check_call(cmd, shell = True, env = os.environ) 
     assert os.path.exists(YARN_JAR_PATH), "failed to build rabit-yarn.jar, try it manually"
@@ -122,7 +122,8 @@ def submit_yarn(nworker, worker_args, worker_env):
     cmd += ' -jobname %s ' % args.jobname
     cmd += ' -tempdir %s ' % args.tempdir
     cmd += (' '.join(args.command + worker_args))    
-    print cmd
+    if args.verbose != 0:
+        print cmd
     subprocess.check_call(cmd, shell = True, env = env)
 
 tracker.submit(args.nworker, [], fun_submit = submit_yarn, verbose = args.verbose, hostIP = args.host_ip)