Ordering
Message passing: no assumptions on orders across processes except those imposed by send/receive pairs
SAS: How processes see the order of other processes’ references defines semantics of SAS
- Ordering very important and subtle
- Uniprocessors play tricks with ordering to gain parallelism or locality
- These are more important in multiprocessors
- Need to understand which old tricks are valid, and learn new ones
- How programs behave, what they rely on, and hardware implications