move Network method implementations from network.h to network.cpp (fixes #4464) (#4496)

include/LightGBM/network.h

@@ -100,9 +100,9 @@ class Network {
   /*! \brief Free this static class */
   static void Dispose();
   /*! \brief Get rank of this machine */
-  static inline int rank();
+  static int rank();
   /*! \brief Get total number of machines */
-  static inline int num_machines();
+  static int num_machines();
 
   /*!
   * \brief Perform all_reduce. if data size is small,
@@ -312,14 +312,6 @@ class Network {
   static THREAD_LOCAL AllgatherFunction allgather_ext_fun_;
 };
 
-inline int Network::rank() {
-  return rank_;
-}
-
-inline int Network::num_machines() {
-  return num_machines_;
-}
-
 }  // namespace LightGBM
 
 #endif   // LightGBM_NETWORK_H_

src/network/network.cpp

@@ -317,4 +317,12 @@ void Network::ReduceScatterRing(char* input, comm_size_t, int type_size,
   std::memcpy(output, input + block_start[rank_], block_len[rank_]);
 }
 
+int Network::rank() {
+  return rank_;
+}
+
+int Network::num_machines() {
+  return num_machines_;
+}
+
 }  // namespace LightGBM