Move __MPI guards inside Parallel_Common bcast functions

Restructure parallel_common.cpp following parallel_reduce.cpp style:
the file-level #ifdef around all 11 bcast_* definitions is replaced
by function-body guards, so serial builds get no-op definitions
instead of link errors. Callers no longer need #ifdef __MPI around
bcast calls (consistent with Parallel_Reduce::reduce_* usage); the
guard previously restored around bcast_bool in to_w90.cpp is removed
again as the net change there is zero.

This fixes the "build without MPI" link failure reported by CI:
undefined reference to Parallel_Common::bcast_bool(bool&).

- Verified: incremental build with MPI passes with no errors;
  g++ -fsyntax-only of parallel_common.cpp without __MPI passes

Author: abacus_fixer

source/source_base/parallel_common.cpp

@@ -6,63 +6,79 @@
 
 #include <cstring>
 
-#ifdef __MPI
 void Parallel_Common::bcast_string(std::string& object) // Peize Lin fix bug 2019-03-18
 {
+#ifdef __MPI
     int size = object.size();
     MPI_Bcast(&size, 1, MPI_INT, 0, MPI_COMM_WORLD);
-    
+
     int my_rank;
     MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
-    
+
     if (0 != my_rank)
     {
         object.resize(size);
     }
 
     MPI_Bcast(&object[0], size, MPI_CHAR, 0, MPI_COMM_WORLD);
+#endif
     return;
 }
 
 void Parallel_Common::bcast_string(std::string* object, const int n) // Peize Lin fix bug 2019-03-18
 {
+#ifdef __MPI
     for (int i = 0; i < n; i++)
         bcast_string(object[i]);
+#endif
     return;
 }
 
 void Parallel_Common::bcast_complex_double(std::complex<double>& object)
 {
+#ifdef __MPI
     MPI_Bcast(&object, 1, MPI_DOUBLE_COMPLEX, 0, MPI_COMM_WORLD);
+#endif
 }
 
 void Parallel_Common::bcast_complex_double(std::complex<double>* object, const int n)
 {
+#ifdef __MPI
     MPI_Bcast(object, n, MPI_DOUBLE_COMPLEX, 0, MPI_COMM_WORLD);
+#endif
 }
 
 void Parallel_Common::bcast_double(double& object)
 {
+#ifdef __MPI
     MPI_Bcast(&object, 1, MPI_DOUBLE, 0, MPI_COMM_WORLD);
+#endif
 }
 
 void Parallel_Common::bcast_double(double* object, const int n)
 {
+#ifdef __MPI
     MPI_Bcast(object, n, MPI_DOUBLE, 0, MPI_COMM_WORLD);
+#endif
 }
 
 void Parallel_Common::bcast_int(int& object)
 {
+#ifdef __MPI
     MPI_Bcast(&object, 1, MPI_INT, 0, MPI_COMM_WORLD);
+#endif
 }
 
 void Parallel_Common::bcast_int(int* object, const int n)
 {
+#ifdef __MPI
     MPI_Bcast(object, n, MPI_INT, 0, MPI_COMM_WORLD);
+#endif
 }
 
 void Parallel_Common::bcast_bool(bool& object)
 {
+#ifdef __MPI
     int swap = object;
     int my_rank;
     MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
@@ -71,11 +87,12 @@ void Parallel_Common::bcast_bool(bool& object)
     MPI_Bcast(&swap, 1, MPI_INT, 0, MPI_COMM_WORLD);
     if (my_rank != 0)
         object = static_cast<bool>(swap);
+#endif
 }
 
 void Parallel_Common::bcast_char(char* object, const int n)
 {
+#ifdef __MPI
     MPI_Bcast(object, n, MPI_CHAR, 0, MPI_COMM_WORLD);
-}
-
 #endif
+}