Libraries and communicators

Libraries and Communicators

• Different phases of an application are assigned different contexts to avoid their messages being confused.
• Library routines need to be passed a communicator for use within the routine.
• Note that use of communicators in library calls does not always guarantee safety. Two successive calls using the same communicator can result in one call receiving messages from the other if the call performs wildcarded receives. This is called ``back-masking,'' and can be prevented by inserting a barrier at the end of the library call.