The R 2.15 release notes and the documentation of makePSOCKCluster state that communication can be better if useXDR = FALSE, but that that setting can only be used if all nodes are little-endian.

1. Does the documentation mean all nodes in the cluster AND the master (the instance that created the cluster and is making calls on that cluster) must have the same endianness?

2. Is the practical implication here that useXDR = FALSE is appropriate when all nodes are running on the same OS, but not appropriate in a mixed-mode environment (i.e. some Linux, some Windows)?

• r

1. All computers that make up the cluster. Information is serialized between the master and all nodes, so byte order matters.
2. It will be fine on multiple OS. Whether a computer is big or little endian is determined by the hardware, not the software. Most computers are little endian (Sun servers are not).