/[MITgcm]/MITgcm/eesupp/inc/GLOBAL_MAX.h
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revision 1.4 by edhill, Sat Mar 27 03:51:50 2004 UTC revision 1.5 by jmc, Wed Jun 10 03:45:11 2009 UTC
# Line 6  C     !INTERFACE: Line 6  C     !INTERFACE:
6  C     include "GLOBAL_MAX.h"  C     include "GLOBAL_MAX.h"
7  C     !DESCRIPTION:  C     !DESCRIPTION:
8  C     *==========================================================*  C     *==========================================================*
9  C     | GLOBAL\_MAX.h                                                C     | GLOBAL\_MAX.h
10  C     | o Globals used by Fortran global max routine.              C     | o Globals used by Fortran global max routine.
11  C     *==========================================================*  C     *==========================================================*
12  C     | The global max shared memory scheme uses global heap data  C     | The global max shared memory scheme uses global heap data
13  C     | structures (.i.e COMMON blocks ). Each thread writes to    C     | structures (.i.e COMMON blocks ). Each thread writes to
14  C     | an its own element of the shared memory array and then      C     | an its own element of the shared memory array and then
15  C     | one thread reads all the entries and maxs them. The max    C     | one thread reads all the entries and maxs them. The max
16  C     | result is then read by all threads.                        C     | result is then read by all threads.
17  C     | Remember - you are working with regions of memory that      C     | Remember - you are working with regions of memory that
18  C     | are being updated concurrently by different threads.        C     | are being updated concurrently by different threads.
19  C     | What happens, when it happens and who gets to see what      C     | What happens, when it happens and who gets to see what
20  C     | happens at what stage depends on the computer systems      C     | happens at what stage depends on the computer systems
21  C     | memory model. Every computer has a different memory model  C     | memory model. Every computer has a different memory model
22  C     | and they are never simple. In all current platforms it is  C     | and they are never simple. In all current platforms it is
23  C     | possible for one thread to see events happening in a        C     | possible for one thread to see events happening in a
24  C     | different order from the order they are written in the      C     | different order from the order they are written in the
25  C     | code.                                                      C     | code.
26  C     | Unless you understand this it is not a good idea to        C     | Unless you understand this it is not a good idea to
27  C     | make modifications te way these header files are setup or  C     | make modifications te way these header files are setup or
28  C     | the way the global sum routines work.                      C     | the way the global max routines work.
29  C     *==========================================================*  C     *==========================================================*
30  CEOP  CEOP
31        COMMON / GMAX_COMMON_R8 / phiGMRL        COMMON / GMAX_COMMON_R8 / phiGMR8
32        Real*8  phiGMRL(lShare8, MAX_NO_THREADS )        Real*8  phiGMR8(lShare8, 0:MAX_NO_THREADS )
33    
34        COMMON / GMAX_COMMON_R4 / phiGMRS        COMMON / GMAX_COMMON_R4 / phiGMR4
35        Real*4  phiGMRS(lShare4, MAX_NO_THREADS )        Real*4  phiGMR4(lShare4, 0:MAX_NO_THREADS )
36    
37        COMMON / GMAX_COMMON_I  / phiGMI        COMMON / GMAX_COMMON_I  / phiGMI
38        INTEGER phiGMI (lShare4, MAX_NO_THREADS )        INTEGER phiGMI (lShare4, 0:MAX_NO_THREADS )
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