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Design Issues
- Need to understand architectural components that affect software
- Compiler , library, program
- User/system interface and hw/ sw interface
- How programming models efficiently talk to the communication architecture?
- How to implement efficient primitives in the communication layer?
- In a nutshell, what issues of a parallel machine will affect the performance of the parallel applications?
- Naming, Operations, Ordering, Replication, Communication cost
Naming
- How are the data in a program referenced?
- In sequential programs a thread can access any variable in its virtual address space
- In shared memory programs a thread can access any private or shared variable (same load/store model of sequential programs)
- In message passing programs a thread can access local data directly
- Clearly, naming requires some support from hw and OS
- Need to make sure that the accessed virtual address gets translated to the correct physical address
Operations
- What operations are supported to access data?
- For sequential and shared memory models load/store are sufficient
- For message passing models send/receive are needed to access remote data
- For shared memory, hw (essentially the CA) needs to make sure that a load/store operation gets correctly translated to a message if the address is remote
- For message passing, CA or the message layer needs to copy data from local memory and initiate send, or copy data from receive buffer to local memory
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