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C $Header: /u/gcmpack/models/MITgcmUV/eesupp/inc/BAR2.h,v 1.1 1998/09/29 18:54:25 cnh Exp $ |
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C $Name: $ |
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1.1 |
C |
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C /==========================================================\ |
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C | BAR2.h | |
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C | o Globals used by BAR2 Fortran barrier routine. | |
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C |==========================================================| |
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C | These variables support a simple Fortran shared memory | |
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C | barrier routine. They do busy waiting, that is the | |
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C | thread that is waiting sits in a tight loop reading | |
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C | some memory location and waiting for all other threads. | |
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C | On some systems this is sometimes a good method to use. | |
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C | On the T3E memory is not shared so the routine should | |
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C | use the T3E "eureka" barriers. On CRAY and NEC there are | |
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C | hardware barriers that are accessed through a compiler | |
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C | directives. Finally proper multi-threading compilers | |
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C | support barrier compile directives - sometimes these | |
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C | are good, sometimes they are lousy. | |
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C | The barrier mechanism is used as follows | |
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C | 1. In the single-threaded part of the code | |
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C | CALL BAR2_INIT | |
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C | on CRAY, NEC this routine does nothing | |
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C | on T3E there is no single-threaded code | |
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C | but there may be barrier initialisation - | |
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C | need to check. | |
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C | 2. When we need to synchronize everybody just | |
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C | CALL BAR2( myThid ) | |
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C | where myThid is myThreadId | |
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C | on CRAY, NEC FBAR will just do C$DIR BARRIER | |
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C | or CALL BARRIER or the like. | |
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C | on T3E FBAR does CALL BARRIER(...) or something | |
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C | need to check this. | |
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C \==========================================================/ |
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COMMON /BAR2_BUFFER_I/ |
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& BAR2_level, |
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& BAR2_barrierCount, |
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& BAR2_spinsCount, BAR2_spinsMax, BAR2_spinsMin |
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INTEGER BAR2_level(cacheLineSize/4,MAX_NO_THREADS) |
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INTEGER BAR2_barrierCount(cacheLineSize/4,MAX_NO_THREADS) |
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INTEGER BAR2_spinsCount(cacheLineSize/4,MAX_NO_THREADS) |
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INTEGER BAR2_spinsMax(cacheLineSize/4,MAX_NO_THREADS) |
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INTEGER BAR2_spinsMin(cacheLineSize/4,MAX_NO_THREADS) |
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COMMON /BAR2_L/ bar2CollectStatistics |
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LOGICAL bar2CollectStatistics |
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