Puzzled about communications between node(s) and host
 

In parallelization of udf, I noticed the following paragraphy in "ufd manual":
"High-level communication macros of the form node to host... and host to node...
are typically used when you want to send data from the host to all of the compute nodes,
or from node-0 to the host. You cannot, however, use these high-level macros when you
need to pass data between compute nodes, or pass data from all of the compute nodes to
compute node-0. In these cases, you can use special message passing macros."

Also, in this udf manual, there is an udf example: Global Summation of Pressure on a Face Zone and its Area Average Computation. In this example, I believe there is need to send the data from all the nodes to node-0, but still it used node_to_host_real_2(,), which is conflicting with the above statement from the same manual.

I'm confused right now, so which way should I follow? To use node_to_host_real or use, say, PRF_CSEND_REAL(to, buffer, nelem, tag)
PRF_CRECV_REAL(from, buffer, nelem, tag)?

Please help, thanks a million!