BMI provides seperate API functions for posting contiguous and noncontiguous buffers for communication. Noncontiguous buffers are represented as arrays of buffer pointers and sizes, and are handled by functions with the _list suffix.
List I/O is useful when a user wishes to send from or receive data into multiple memory regions using a single network message. This is convenient for mapping network I/O to parallel I/O access patterns.
Messages posted using the list interface are completely compatible with contiguous messages on the peer side. Regions do not have to match between sender and receiver, nor do they both have to be discontiguous. The aggregate size of the message does need to match, however. The list functions support all of the features of the ``normal'' API, including short messages.
The intention is for method level support of list messages to be optional; if a method does not implement this functionality, then the method control layer of BMI will emulate it by packing and unpacking regions using contiguous intermediate buffers. This is obviously a performance penalty, but will ensure correct behavior when a native method cannot easily handle discontiguous memory regions.