middle version

src/sync/sync.cpp

@@ -5,29 +5,6 @@
 namespace xgboost {
 namespace sync {
 
-// code for reduce handle
-ReduceHandle::ReduceHandle(void) : handle(NULL) {
-}
-ReduceHandle::~ReduceHandle(void) {
-  if (handle != NULL) {
-    MPI::Op *op = reinterpret_cast<MPI::Op*>(handle);
-    op->Free();
-    delete op;
-  }
-}
-void ReduceHandle::Init(ReduceFunction redfunc, bool commute) {
-  utils::Assert(handle == NULL, "cannot initialize reduce handle twice");
-  MPI::Op *op = new MPI::Op();
-  MPI::User_function *pf = reinterpret_cast<MPI::User_function*>(redfunc);
-  op->Init(pf, commute);
-  handle = op;
-}
-void ReduceHandle::AllReduce(void *sendrecvbuf, size_t n4byte) {
-  utils::Assert(handle != NULL, "must intialize handle to call AllReduce");  
-  MPI::Op *op = reinterpret_cast<MPI::Op*>(handle);
-  MPI::COMM_WORLD.Allreduce(MPI_IN_PLACE, sendrecvbuf, n4byte, MPI_INT, *op);
-}
-
 int GetRank(void) {
   return MPI::COMM_WORLD.Get_rank();
 }
@@ -57,5 +34,37 @@ void AllReduce<float>(float *sendrecvbuf, int count, ReduceOp op) {
   AllReduce_(sendrecvbuf, count, MPI::FLOAT, op);
 }
 
+void Bcast(std::string *sendrecv_data, int root) {
+  unsigned len = static_cast<unsigned>(sendrecv_data->length());
+  MPI::COMM_WORLD.Bcast(&len, 1, MPI::UNSIGNED, root);
+  sendrecv_data->resize(len);
+  if (len != 0) {
+    MPI::COMM_WORLD.Bcast(&(*sendrecv_data)[0], len, MPI::CHAR, root);  
+  }
+}
+
+// code for reduce handle
+ReduceHandle::ReduceHandle(void) : handle(NULL) {
+}
+ReduceHandle::~ReduceHandle(void) {
+  if (handle != NULL) {
+    MPI::Op *op = reinterpret_cast<MPI::Op*>(handle);
+    op->Free();
+    delete op;
+  }
+}
+void ReduceHandle::Init(ReduceFunction redfunc, bool commute) {
+  utils::Assert(handle == NULL, "cannot initialize reduce handle twice");
+  MPI::Op *op = new MPI::Op();
+  MPI::User_function *pf = reinterpret_cast<MPI::User_function*>(redfunc);
+  op->Init(pf, commute);
+  handle = op;
+}
+void ReduceHandle::AllReduce(void *sendrecvbuf, size_t n4byte) {
+  utils::Assert(handle != NULL, "must intialize handle to call AllReduce");  
+  MPI::Op *op = reinterpret_cast<MPI::Op*>(handle);
+  MPI::COMM_WORLD.Allreduce(MPI_IN_PLACE, sendrecvbuf, n4byte, MPI_INT, *op);
+}
+
 }  // namespace sync
 }  // namespace xgboost

src/sync/sync.h

@@ -18,11 +18,39 @@ enum ReduceOp {
   kBitwiseOR
 };
 
-typedef void (ReduceFunction) (const void *src, void *dst, int len);
+/*! \brief get rank of current process */
+int GetRank(void);
+/*! \brief intiialize the synchronization module */
+void Init(int argc, char *argv[]);
+/*! \brief finalize syncrhonization module */
+void Finalize(void);
 
-/* !\brief handle for customized reducer */
+/*!
+ * \brief in-place all reduce operation 
+ * \param sendrecvbuf the in place send-recv buffer
+ * \param count count of data
+ * \param op reduction function
+ */
+template<typename DType>
+void AllReduce(DType *sendrecvbuf, int count, ReduceOp op);
+
+/*!
+ * \brief broadcast an std::string to all others from root
+ * \param sendrecv_data the pointer to send or recive buffer,
+ *                      receive buffer does not need to be pre-allocated
+ *                      and string will be resized to correct length
+ * \param root the root of process
+ */
+void Bcast(std::string *sendrecv_data, int root);
+
+/*! 
+ * \brief handle for customized reducer 
+ * user do not need to use this, used Reducer instead
+ */
 class ReduceHandle {
  public:
+  // reduce function
+  typedef void (ReduceFunction) (const void *src, void *dst, int len);
   // constructor
   ReduceHandle(void);
   // destructor
@@ -41,22 +69,8 @@ class ReduceHandle {
   void *handle;
 };
 
-/*! \brief get rank of current process */
-int GetRank(void);
-/*! \brief intiialize the synchronization module */
-void Init(int argc, char *argv[]);
-/*! \brief finalize syncrhonization module */
-void Finalize(void);
+// ----- extensions for ease of use ------
 /*!
- * \brief in-place all reduce operation 
- * \param sendrecvbuf the in place send-recv buffer
- * \param count count of data
- * \param op reduction function
- */
-template<typename DType>
-void AllReduce(DType *sendrecvbuf, int count, ReduceOp op);
-
-/*! 
  * \brief template class to make customized reduce and all reduce easy  
  * Do not use reducer directly in the function you call Finalize, because the destructor can happen after Finalize
  * \tparam DType data type that to be reduced