Part Ill: Parallel Programming models The Shared-Variable model 1. Basic Concept: The shared-variable programming is the native model for PVP, SMP and DSM machines. THere is an ANSI X3H5 standard. The portability of programs is problematic 2. Features Multiple threads: A shared variable program uses either SPMD(Single- Program-Multiple-Data)or MPMD (Multiple-Program-Multiple-Data) Asynchronous: Each process executes at its on pace Explicit synchronization: special synchronous operations(barrier, lock, critical region, event)are use Single address space: all variables reside in a single address space. Implicit data and computation distribution: because data can be considered in SM. there is no need to explicitly distribute data and computation. Implicit communication: communication is done implicitly through reading/ writing of shared variables NHPCC(Hefei)·USTC· CHINA glchenaustc edu.ciNHPCC(Hefei) •USTC •CHINA glchen@ustc.edu.cn The Shared-Variable Model Part III:Parallel Programming Models 3 - 3