Parallel Programming

Prolog: Why Bother?

• As an architect why should you be concerned with parallel programming?
  • Understanding program behavior is very important in developing high-performance computers
  • An architect designs machines that will be used by the software programmers: so need to understand the needs of a program
  • Helps in making design trade-offs and cost/performance analysis i.e. what hardware feature is worth supporting and what is not
  • Normally an architect needs to have a fairly good knowledge in compilers and operating systems

Agenda

• Steps in writing a parallel program
• Example

Writing a Parallel Program

• Start from a sequential description
• Identify work that can be done in parallel
• Partition work and/or data among threads or processes
  • Decomposition and assignment
• Add necessary communication and synchronization
  • Orchestration
• Map threads to processors ( Mapping )
• How good is the parallel program?
  • Measure speedup = sequential execution time/parallel execution time = number of processors ideally