Squashed 'subtree/rabit/' changes from 1bb8fe9..4db0a62

4db0a62 bugfix of lazy prepare
87017bd license
dc703e1 license
c171440 change license to bsd
7db2070 Update README.md
581fe06 add mocktest
d2f252f ok
4a5b9e5 add all
12ee049 init version of lbfgs
37a2837 complete lbfgs solver
6ade7cb complete lbfgs

git-subtree-dir: subtree/rabit
git-subtree-split: 4db0a62a06

src/allreduce_robust.cc

@@ -77,7 +77,10 @@ void AllreduceRobust::Allreduce(void *sendrecvbuf_,
                                 PreprocFunction prepare_fun,
                                 void *prepare_arg) {
   // skip action in single node
-  if (world_size == 1) return;
+  if (world_size == 1) {
+    if (prepare_fun != NULL) prepare_fun(prepare_arg);
+    return;
+  }
   bool recovered = RecoverExec(sendrecvbuf_, type_nbytes * count, 0, seq_counter);
   // now we are free to remove the last result, if any
   if (resbuf.LastSeqNo() != -1 &&

src/engine_empty.cc

@@ -92,6 +92,7 @@ void Allreduce_(void *sendrecvbuf,
                 mpi::OpType op,
                 IEngine::PreprocFunction prepare_fun,
                 void *prepare_arg) {
+  if (prepare_fun != NULL) prepare_fun(prepare_arg);
 }
 
 // code for reduce handle
@@ -106,6 +107,8 @@ void ReduceHandle::Init(IEngine::ReduceFunction redfunc, size_t type_nbytes) {}
 void ReduceHandle::Allreduce(void *sendrecvbuf,
                              size_t type_nbytes, size_t count,
                              IEngine::PreprocFunction prepare_fun,
-                             void *prepare_arg) {}
+                             void *prepare_arg) {
+  if (prepare_fun != NULL) prepare_fun(prepare_arg);
+}
 }  // namespace engine
 }  // namespace rabit