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C $Header: /u/gcmpack/MITgcm/eesupp/inc/GLOBAL_MAX.h,v 1.4 2004/03/27 03:51:50 edhill Exp $ |
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C $Name: $ |
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CBOP |
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C !ROUTINE: GLOBAL_MAX.h |
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C !INTERFACE: |
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C include "GLOBAL_MAX.h" |
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C !DESCRIPTION: |
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C *==========================================================* |
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C | GLOBAL\_MAX.h |
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C | o Globals used by Fortran global max routine. |
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C *==========================================================* |
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C | The global max 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 maxs them. The max |
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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 max routines work. |
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C *==========================================================* |
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CEOP |
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COMMON / GMAX_COMMON_R8 / phiGMR8 |
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Real*8 phiGMR8(lShare8, 0:MAX_NO_THREADS ) |
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COMMON / GMAX_COMMON_R4 / phiGMR4 |
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Real*4 phiGMR4(lShare4, 0:MAX_NO_THREADS ) |
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COMMON / GMAX_COMMON_I / phiGMI |
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INTEGER phiGMI (lShare4, 0:MAX_NO_THREADS ) |
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