C $Header: /u/gcmpack/MITgcm/eesupp/inc/GLOBAL_MAX.h,v 1.5 2009/06/10 03:45:11 jmc Exp $
C $Name: $
CBOP
C !ROUTINE: GLOBAL_MAX.h
C !INTERFACE:
C include "GLOBAL_MAX.h"
C !DESCRIPTION:
C *==========================================================*
C | GLOBAL\_MAX.h
C | o Globals used by Fortran global max routine.
C *==========================================================*
C | The global max shared memory scheme uses global heap data
C | structures (.i.e COMMON blocks ). Each thread writes to
C | an its own element of the shared memory array and then
C | one thread reads all the entries and maxs them. The max
C | result is then read by all threads.
C | Remember - you are working with regions of memory that
C | are being updated concurrently by different threads.
C | What happens, when it happens and who gets to see what
C | happens at what stage depends on the computer systems
C | memory model. Every computer has a different memory model
C | and they are never simple. In all current platforms it is
C | possible for one thread to see events happening in a
C | different order from the order they are written in the
C | code.
C | Unless you understand this it is not a good idea to
C | make modifications te way these header files are setup or
C | the way the global max routines work.
C *==========================================================*
CEOP
COMMON / GMAX_COMMON_R8 / phiGMR8
Real*8 phiGMR8(lShare8, 0:MAX_NO_THREADS )
COMMON / GMAX_COMMON_R4 / phiGMR4
Real*4 phiGMR4(lShare4, 0:MAX_NO_THREADS )
COMMON / GMAX_COMMON_I / phiGMI
INTEGER phiGMI (lShare4, 0:MAX_NO_THREADS )