Solved by takafusui in post #2 
              
              
                Sorry… I messed up. The correct syntax is 
if rank == 0:
    x = torch.tensor([1], dtype=torch.float64)
if rank != 0:
    x = None
x = comm.bcast(x, root=0)
print("Rank {} recieves {}".format(rank, x))

and now it works as I intend: 
Rank 4 recieves tensor([1.], dtype=torch.float64)
Rank 9 recieves …