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Models and Languages

Models

• Model - user's view of a machine

• Explicit or implicit representation of parallelism

• MIMD vs. SIMD

• MIMD SM vs MIMD DM

• Communication methods
  • message passing

  • tuple space

  • virtual shared memory (VSM)

Programming

Languages

• Level of abstraction

• Ease of use
  • efficiency

  • clarity

  • portability

• Areas of responsibility
  • user

  • system

Language Types

• Conventional sequential
  • parallelism implemented by the compiler

  • can be good but not good enough

• Extended languages
  • Fortran 90, High Performance Fortran

  • 3L languages

  • Message Passing libraries: PVM, MPI, ...

• New Parallel Languages
  • Occam

  • Linda

• Libraries of parallel code
  • poor efficiency

  • series of parallel section linked by sequential code

Language Developments

• Parallelizing Compilers
  • autoparallelisation (available but poor)

  • Data dependency analysis and reduction

  • paralysing compilers

  • 2nd best solution (eg. DO is essentially a sequential construct)

• New languages
  • "dusty deck" conversion

  • retrain staff

  • adherence to standards

• Convergence of hardware and software