use cpp macro to exclude collectives from the build in serial mode

Author: milancurcic

src/lib/mod_layer.f90

@@ -103,7 +103,9 @@ subroutine db_co_sum(db)
     type(array1d), allocatable, intent(in out) :: db(:)
     integer(ik) :: n
     do n = 2, size(db)
+#ifdef CAF
       call co_sum(db(n) % array)
+#endif
     end do
   end subroutine db_co_sum
 
@@ -112,7 +114,9 @@ subroutine dw_co_sum(dw)
     type(array2d), allocatable, intent(in out) :: dw(:)
     integer(ik) :: n
     do n = 1, size(dw) - 1
+#ifdef CAF
       call co_sum(dw(n) % array)
+#endif
     end do
   end subroutine dw_co_sum
 

src/lib/mod_network.f90

@@ -226,8 +226,10 @@ subroutine sync(self, image)
     integer(ik) :: n
     if (num_images() == 1) return
     layers: do n = 1, size(self % dims)
+#ifdef CAF
       call co_broadcast(self % layers(n) % b, image)
       call co_broadcast(self % layers(n) % w, image)
+#endif
     end do layers
   end subroutine sync