2.1 Characteristics
- Performed on a group of processes,
- identified by a communicator
- Substitute for a sequence of point-to-point calls
- Communications are locally blocking
- Synchronization is not guaranteed
- (implementation dependent)
- Some routines use a root process
- to originate or receive all data
- Data amounts must exactly match
- Many variations to basic categories
- No message tags are needed
MPI collective communication routines differ in many ways from MPI point-to-point communication routines, which were introduced in MPI Point to Point Communication I. Here are the characteristics of MPI collective communication routines:
- Involve coordinated communication within a group of processes identified by an MPI communicator
- Substitute for a more complex sequence of point-to-point calls
- All routines block until they are locally complete
- Communications may, or may not, be synchronized (implementation dependent)
- In some cases, a root process originates or receives all data
- Amount of data sent must exactly match amount of data specified by receiver
- Many variations to basic categories
- No message tags are needed
MPI collective communication can be divided into three subsets:
- synchronization
- data movement
- global computation
which are covered in the following three sections.
