Reducing Overhead
Can reduce no. of messages m or overhead per message o
o is usually determined by hardware or system software
- Program should try to reduce m by coalescing messages
- More control when communication is explicit
Coalescing data into larger messages:
- Easy for regular, coarse-grained communication
- Can be difficult for irregular, naturally fine-grained communication
- may require changes to algorithm and extra work
- coalescing data and determining what and to whom to send
- will discuss more in implications for programming models later