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C $Header: /u/gcmpack/models/MITgcmUV/eesupp/inc/Attic/GLOBAL_SUM.h,v 1.1.2.1 2001/04/12 10:52:48 cnh Exp $ |
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C $Name: pre38-close $ |
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C |
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C /==========================================================\ |
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C | GLOBA:_SUM.h | |
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C | o Globals used by Fortran global sum routine. | |
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C |==========================================================| |
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C | The global sum shared memory scheme uses global heap data| |
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C | structures (.i.e COMMON blocks ). Each thread writes to | |
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C | an its own element of the shared memory array and then | |
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C | one thread reads all the entries and sums them. The sum | |
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C | result is then read by all threads. | |
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C | Remember - you are working with regions of memory that | |
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C | are being updated concurrently by different threads. | |
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C | What happens, when it happens and who gets to see what | |
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C | happens at what stage depends on the computer systems | |
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C | memory model. Every computer has a different memory model| |
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C | and they are never simple. In all current platforms it is| |
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C | possible for one thread to see events happening in a | |
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C | different order from the order they are written in the | |
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C | code. | |
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C | Unless you understand this it is not a good idea to | |
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C | make modifications te way these header files are setup or| |
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C | the way the global sum routines work. | |
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C \==========================================================/ |
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COMMON / GSUM_COMMON_R8 / phiGSRL |
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Real*8 phiGSRL(lShare8, MAX_NO_THREADS ) |
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COMMON / GSUM_COMMON_R4 / phiGSRS |
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Real*4 phiGSRS(lShare4, MAX_NO_THREADS ) |
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COMMON / GSUM_COMMON_I / phiGSI |
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INTEGER phiGSI (lShare4, MAX_NO_THREADS ) |
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