lect08-sgi

lect08-sgi - Notes ! OpenMP assignment due next Wednesday !...

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CMSC 714 Lecture 8 SGI Origin 2000 and Altix Alan Sussman 2 CMSC 714 - Alan Sussman & Jeffrey K. Hollingsworth Notes ! OpenMP assignment due next Wednesday – probably not a good idea to compile for profiling (with –pg) and for OpenMP at same time • can use omp_get_wtime() to time parts of your OpenMP() code – OK to call from different threads – other questions? ! MPI project grades by end of week ! Sample topics for group project posted soon 3 Shared Memory Multiprocessors ! Cache coherence – to keep different copies of same memory location (data block) the same – caching causes the problem, but is needed for performance ! Snooping vs. directory-based coherence – shared medium (bus or switched network) vs. distributed directory to keep track of shared data blocks – either way, all memory accesses are to local copies near a processor, and data blocks change state and move around to where they are needed – state of each block kept track of with a finite state machine
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This note was uploaded on 01/12/2012 for the course CMSC 714 taught by Professor Staff during the Fall '07 term at Maryland.

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lect08-sgi - Notes ! OpenMP assignment due next Wednesday !...

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